The Pennsylvanian-Permian Vegetational Transition: A Terrestrial Analogue to the Onshore-Offshore Hypothesis STOR
William A. DiMichele; Richai'd B. Aronson
Evolution, Vol. 46, No. 3 (Jun., 1992), 807-824.
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http: //w w w .j s tor. org/ WedSep 1 12:53:14 2004 EwluXion. '16(3), 1552, pp. 807-834
THE PENNSYLVANIAN-PERMIAN VEGETATIONAL TRANSITION: A TERRESTRIAL ANALOGUE TO THE ONSHORE-OFFSHORE HYPOTHESIS
WILLIAM A. DIMKHELE AND RKHARD B. ARONSON Department of Paieabiology, National Museum of Natural History, Smithsonian Instiimion, Washington, DC 20560 USA
Abstract. —An analysis of 68 floras from the Pennsylvanian and Early Permian of Euramerica reveals distinct patterns of environmental distribution. Wetland assemblages are the most com- monly encountered floras from the Early and Middle Pennsylvanian. Floras from drier habitats characterize the Permian. Both wetland and dry-site floras occur in the Late Pennsylvanian, but floristic overlap is minimal, which implies strong environmental controls on the distributions of the component species. Drier habitats appear to be the sites of first appearance of orders that become prominent during the Late Permian and Mesozoic. Higher taxa originated in physically heterogeneous, drier habitats, which were geographically marginal throughout most of the Penn- sylvanian. They then moved into the lowlands during periods of climatic drying in the Permian, replacing older wetland vegetation. This pattern is analogous to the marine onshore-oflfehore pattern of origination and migration. The derivation of Mesozoic wetland clades from the Permian dry- lowland vegetation completes the parallel. The similarities of the marine and terrestrial patterns suggest that the combination of evolutionary opportunity, created by physical heterogeneity of the environment, and migrational opportunity, created by changing extrinsic conditions, may be un- derlying factors that transcend the specifics of organism and environment.
Key words—MacTOtvahilion, onshore-offshore hypothesis, paleoecology, Pennsylvanian, Permian, upland flora.
Received July 2, 1990. Accepted October 29, 1991.
Botanists have long regarded semixeric to dence is relatively recent and continues to xeric habitats as sites favoring the survival accrue. The best documented Paleozoic ex- of morphological novelties (Stebbins, 1952; amples are the conifers (Scott and Chaloner, Axelrod, 1972). In contrast, swamps and 1983; Lyons and Darrah, 1989), eariy fili- associated wetlands have been character- calean fems (Scott and Galtier, 1985), cy- ized as refugia where archaic taxa and com- cads (Mamay, 1976, 1990; Leary, 1990), munities survive for long periods of geo- peltasperms (Kerp, 1988di), and gigantop- logic time (Knoll, 1985; DiMichele et al., terids (Mamay, 1986, 1988). Others that also 1987). The persistence of archaic species and appear to fit the pattern include the cordai- communities in the wet lowlands is a gen- talean gymnosperms (Chaloner, 1958), the eralization drawn from the vast majority of Ginkgoales (Mamay, 1981), the Noeggera- paleobotanical data (for Paleozoic data see thiales (Leary and Pfefferkom, 1977), and Davies, 1929; Oshurkova, 1974, 1978; glossopterids (Retallack and Dilcher, 1981). Havlena, 1970; Phillips etal., 1985). On the Early seed plants, although they may have other hand, the inference of evolutionary originated in Late Devonian wetlands (Gil- innovation in extrabasinal, peripheral, or lespieetal., 1981), radiated subsequently in upland areas (Mapes and Gastaldo, 1987, more xeric habitats (Rothwell and Scheck- discuss terminology) developed primarily ler, 1988; Bateman and Rothwell, 1990; Re- as an explanation for the absence of ex- tallack and Dilcher, 1988). A variety of pected intermediate forms linking the high- enigmatic forms, including genera with un- er taxa found in lowland floras (e.g., Arnold, certain affinities also occur first in what ap- 1947; Axelrod, 1967; Stidd, 1980). pear to be moisture-stressed habitats of the The earliest evidence of most major vas- Early Permian {Glenopteris: Sellards, 1908; cular plant groups (orders approximately) Yakia: White, 1929; RmselUes: Mamay, suggests that they originated or diversified 1968; Wattia: Mamay, 1967; callipterid in habitats that were periodically moisture- complex: Kerp, 1988i; Kerp and Haubold, stressed and often peripheral to major ba- 1988). sinal wetlands. For many groups this evi- In this paper we examine the Pennsyl- 807 808 W, A. DiMICHELE AND R. B. ARONSON vanian-Permian vegetational transition as a of lithologies, or characteristic of a time unit possible analogue of the marine onshore- were rejected from the data base because ofFshore hypothesis. Many of the genera, the degree of species cooccurrence could not families and orders that originated in mois- be assessed reliably. ture-limited habitats during the late Paleo- Eighty taxa, identified to genus, or in some zoic were part of a vegetation that replaced cases to generic groups such as "walchians," the archaic wetland floras of the Carbonif- were included in the data base. Although erous tropics as the lowlands dried out. The using genera reduces ecological precision, it new taxa, inhabitants of the new seasonally avoids the inconsistencies in many species- dry lowlands, became the ancestors of the level taxonomies, and provides a conser- dominant early Mesozoic wetland vegeta- vative estimate of distributional patterns. tion. This pattern of lineage and community replacement may be a terrestrial parallel to Environmental Data the "onshore-offshore" patterns detected in The habitat from which a fossil plant as- the Phanerozoic marine record. Major mor- semblage was drawn can be described in a phological innovations in benthic inverte- variety of ways, often in great detail. For brates first appeared in physically hetero- the purpose of this analysis we were con- geneous, disturbed nearshore environments cerned with just two attributes: local mois- and then expanded offshore into more sta- ture hmitation and physical location rela- ble deep-water environments (Jablonski et tive to basinal lowlands. Unfortunately there al., 1983; SepkoskiandSheehan, 1983; Sep- are significant terminological difficulties as- koski and Miller, 1985; Bottjer and Jablon- sociated with the description of these fea- ski, 1988; Jablonski and Bottjer, 1990; Sep- tures, resulting in part from their being con- koski, 1991). Despite possible differences in founded (e.g., all lowlands are wet, all factors mediating the habitat shifts, the sim- uplands are dry). Such problems are dis- ilarities between the marine and terrestrial cussed and partially clarified by Havlena patterns are striking. Both patterns may re- (1970) and Mapes and Gastaldo (1987), but flect a fundamental relationship between considerable confusion remains. evolution and environment. We have avoided the term "stress" due to the ambiguity of its usage (see DiMichele etal., 1987). Swamps, for example, are high- DATA AND ANALYSIS ly "stressful" in the sense of their edaphics; Floristic Data physico-chemical properties of the sub- Roras were compiled from 68 North strate exclude nearly all plants and create a American and European localities, part of sharp, nongradational boundary with sur- a continuous tropical landmass during the rounding habitats (heavy metal-rich sub- late Paleozoic (Ziegler, 1990). The floras strates have the same properties, see Brad- range in age from Early Pennsylvanian to shaw and McNeilly, 1981 and references Late Permian. A "flora" in the sense used therein). Seasonally dry habitats also are here is a collection made from a single de- "stressful," but in a different sense. A gra- positional environment at a single site. A dient exists from habitats or microhabitats site can vary from a meter square prospect with constantly available moisture to those pit to the roof shale of a coal exposed in one that are moisture "stressed." The evolu- strip mine. Floras from depositional envi- tionary response of plants to edaphic stress ronments suggesting a high potential for al- is quite different from their response to lochthonous origin were excluded from con- moisture limitation. Swamps, for example, sideration due to potential mixing of are not centers of evolutionary innovation. vegetational types from edaphically distinct Over geological time they tend to accu- parts of the landscape. Temporal hetero- mulate species that can tolerate such con- geneity and mixing of distinct vegetational ditions, and preserve species associations types therefore are reduced as much as pos- for long periods of time (Knoll, 1985; sible (see Scheihing and Pfefferkom, 1980, DiMichele et al., 1987). Swamps contrast for discussion). Floral lists representative of markedly with moisture-limited regions, in a formation, of a heterogeneous assemblage which high local habitat heterogeneity leads PENNSYLVANIAN-PERMIAN VEGETATIONAL TRANSITION 809 to local floristic variation and significant channel deposits suggest seasonal variations evolutionary opportunity (Axelrod, 1972; in discharge (Kvale and Eggert, 1988; Fish- Stebbms, 1952). baugh et al., 1989). At the opposite extreme, Nearly all the assemblages we analyzed the Hermit Shale flora of Arizona also ap- qualify as lowland in the sense that they are pears to have experienced seasonal fluctu- from depositional basins, probably within ations in stream flow, but superimposed on 100 km of contemporaneous marine con- a much more arid climate, suggested by ditions. Noteworthy exceptions are some molds of salt crystals, alternation of mud- Lower Pennsylvanian floras studied by cracked rocks and plant-bearing siltstones, Leary (1981) and Leary and Pfefferkom and a strongly xeromorphic flora (White, (1977), which appear to beextrabasinal, but 1929). Because these kinds of inferences are still from lowland settings (Pfefferkom, exceptional, we have not focused on the de- 1980). Evidence of true upland floras is in- tails of seasonality. direct; Middle Pennsylvanian conifers, for The following physical criteria were used example, occur as highly fragmentary and to determine the local moisture conditions often fusinized (burned to charcoal) remains of fossil habitats. Wetland paleoenviron- in lowland habitats proximal to contem- ments were considered to be those associ- poraneous, tectonically active, uplifted ar- ated with coals, either as roof shales or un- eas (Scott and Chaloner, 1983). North derclays, or as coming from coal-bearing American conifers display a similar pattern sequences, where high moisture availability of occurrence in the Late Pennsylvanian and hmited seasonality are strongly sug- (Lyons and Darrah, 1989). Overall, how- gested. Well-drained to "dry" paleoenvi- ever, the actual evidence of upland floras, ronments included those a) that are asso- which may have existed as early as the Low- ciated with indicators of a dry season (e.g., er Carboniferous in volcanogenic terrains molds of salt crystals, mudcracks, red col- (Scott and Galtier, 1985; Bateman and oration); b) with sedimentological evidence Rothwell, 1990; Rex and Scott, 1987), is too that stream discharge was seasonal; c) that scattered and fragmentary in the Pennsyl- did not occur in association with coals; and/ vanian and Early Permian to be of value in or d) bearing evidence of local relief suffi- a quantitative analysis. Where Early and cient to create areas with well-drained soil Middle Pennsylvanian plants can be iden- conditions. The inferred moisture regimes tified in environments that suggest mois- were partially corroborated when the mor- ture-limitation (paleosols that formed un- phological characteristics of the floras (par- der dry, seasonal climates, for example), they ticularly the proportion of xeromorphic belong to the same groups that dominate species in the flora, an ataxonomic property) dry habitats in lowlands during the Late were harmonious with the inference. Pennsylvanian and Early Permian. Virtually all the Lower and Middle Penn- Moisture availability was the major phys- sylvanian floras appear to be from very wet ical difference detectable among the floras to mostly wet habitats. Such wetlands are we analyzed. In some instances it was pos- not restricted to swamps, and include a sible to infer distinct seasonality in moisture broad range of poorly drained floodplains, regime, and it is probably through an in- levees, and coastal deposits such as lagoons. crease in seasonality that progressively drier In contrast, the Permian deposits analyzed climates affected regional vegetation in Eur- here all appear to be from seasonally dry america (Cecil, 1990). However, in most in- habitats. The range of variation in the stances seasonality is demonstrated less eas- Permian is much greater than that of the ily than overall moisture limitation from Early and Middle Pennsylvanian. Strati- rainfall and runoff, or limitation by soil graphic overlap of wet and dry floras occurs drainage (Phillips and Peppers, 1984; Win- in the Late Pennsylvanian (see Appendix 3). ston, 1990). For example, the Roaring Creek and Cuticle Coal floras of Indiana are as- Analysis sociated closely with coals in a near-coastal Most statistical analyses were performed environment and clearly formed under hu- with Systat, version 4.1 (Wilkinson, 1988). mid, wet conditions, but contemporaneous The discriminant function analysis was per- 810 W. A. DiMICHELE AND R. B. ARONSON
of the two groups of sites. These statistics are the basis for assessing relative dispersion - 0 among the sites from each type of habitat. 0 p p The results of the ordination were eval- p p p 0 - p 0 CMJ 0 uated further with a discriminant function p x ¥P ''^ PX 0flo"„M analysis in which Permian and Early/Mid- p p ^ dle Pennsylvanian assemblages were treated p WM X E EQ M as separate groups of knowns on which a p p ^ p p discriminant function was based; Late p Pennsylvanian assemblages were classified E as unknowns on the basis of this discrimi- E nant function. Predictor variables (species) p for the discriminant function were chosen -2 -1.S -I -0.5 0 0.5 1 1,5 in a step-wise manner. The effectiveness of FIG, 1. Ordination of 68 Pennsylvanian and Early variables in group separation was measured Permian fossil plant assemblages based on 80 genera or groups of related genera (e.g., conifers). P, Permian in separate analyses with Wilks' Lambda dry lowlands; M, Middle Pennsylvanian wetlands; E, and with Mahalanobis' Distance, which Early Pennsylvanian wetlands. Late Pennsylvanian as- yielded similar results; the results reported semblages are divided into those from coal-bearing here are from the Wilk's Lambda analysis. wetlands (O), and those from dry or seasonally dry Thirty-one variables (species) were dropped habitats TABLE 1. Distribution and analysis of Jaccard coefficients used in calculation of Figure 1. Coeliiciert of Kibitat AT Min Mai M^ln SD Mtdian variitiotv DRY 560 0.00 0.67 0.24 0J4 0.20 0.58 WET 560 0.00 0.78 0.30 0.14 0.29 0.47 confirmed by the discriminant analysis. All tinguishes Permian from Middle and Early 22 of the Upper Pennsylvanian assemblages Pennsylvanian tropical floras. This appar- were classified correctly, that is in accor- ent signal of geological age is probably an dance with their position in the ordination. environmental signal, as indicated by the Analysis of the original Jaccard coeffi- divided affinities of Late Pennsylvanian flo- cient matrix reveals higher average sin^ila^- ras. Indicators of physical conditions, in ity, and a lower coefficient of variation particular the moisture deficit of the land- among the lowland, wetland assemblages scape, strongly suggest increasing moisture than among those from drier habitats of the limitation from the Middle Pennsylvanian Permian and Late Pennsylvanian (Table 1). to the Early Permian in tropical Euramer- This result suggests that wetland assem- ica, probably as a consequence of changing blages have a lower dispersion than dry hab- continental configurations and the degree of itat assemblages. The stratigraphic distri- polar glaciation (Phillips and Peppers, 1984; bution of those taxa with significant runs Ziegler, 1990; citations in Appendix 2 for tests {Table 2) illustrates that wetland and primary data). The patterns of floristic re- dryland sites have distinct compositional lationship, demonstrated in Figure 1 and in patterns, despite some overlap. the results of the subsequent discriminant Taken together, the patterns en^phasize analysis, indicate that the "Permian" low- the coherence and distinctiveness of the land vegetation existed, as a unit, in the plant associations from wetlands and drier drier, marginal areas during the Late Penn- habitats. The greater dissimilarity among sylvanian, if not eariier (Scott and Chaloner, dry-habitat assemblages is expected from 1983;McComas, 1988;Broutinetal., 1990). analyses of modem environments; a greater The uncommon, distinctive Late Pennsyl- range of habit types is included within the vanian floras from drier habitats (Table 2; dry-habitat rubric, and dry habitats are Appendices 1, 2, and 3) contain several of characterized by greater local habitat het- the important basinal Uneages of the Perm- erogeneity, greater opportunity for isola- ian and Mesozoic, specifically Cycadales tion, and perhaps more opportunity for evo- (Spermopteris at Baldwin and Gamett; Pla- lutionary divergence (Axelrod, 1967, 1972; giozamites at Kinney; Charliea at Kinney), del Moral et al., 1985; Mason, 1946; Steb- Coniferales (at all dry sites), possible Gink- bins, 1952). goales (Dicranophyllum at Kinney), and Floras from Late Pennsylvanian and members of the callipterid complex (at all Permian dry habitats also contain more un- dry sites except Kinney, McCoy and 7-11). common genera than do floras from wet- Despite their temporal cooccurrence, dry- lands. Most of these are members of seed- habitat floras are taxonomically and distri- plant clades with distinctive architectures, butionally distinct from wetland assem- recognized as orders that became abundant blages throughout the Pennsylvanian. during the Permian or in the Mesozoic. In- cluded are the Cycadales, Gigantopterida- les, Peltaspermales, Ginkgoales, and a num- DISCUSSION ber of taxa with unclear affinities. Most are The Onshore-Offshore Analogy unknown from Upper Pennsylvanian wet- In 1983, Jablonski and others suggested land assemblages. They appear to have been that major morphological innovations in more narrowly limited ecologically during benthic invertebrates appeared in near-shore the Paleozoic than later. environments and then expanded across the The first axis of the ordination clearly dis- shelf, based on patterns in Cambro-Ordo- 812 w. A. DEMICHELE AND R. B. ARONSON TABLE 2. Scratigraphic distribution of taxa used in analyses. Number of sites in each time interval is listed in parenttieses. An asterisk in the last column denotes a taxon with significant (P < 0,5, two-tailed) runs in its distribution. Ptrrnian Dry SttphatiLatt Wet Stephan[an TaMn (23) (11) (U) WestphaUan Runs Spertnopteris 1 2 0 0 Gigan topteridium 4 0 0 0 * Gigantonodea 2 0 0 0 Xeilleroi>ter\s 1 0 0 0 Catkaysiopteris 2 0 0 0 Delnortea 1 0 0 0 Evohonia 2 0 0 0 « Phasmatocycas 6 0 0 0 « Archaeocycas 1 0 0 0 Cycadosp^dix 1 0 0 0 "cycad" J 0 0 0 Charliea 0 1 0 0 Podozamites 0 I 0 0 RusseliLes 2 0 0 0 Sandrewia 3 0 0 0 Wanin 3 0 0 0 • Tlnsteya I 0 0 0 Yakia 2 0 0 0 Glenopteris 3 0 0 0 • Supaia 4 0 0 0 • Padgettia 1 0 0 0 Plagiozaynites 0 I 0 0 Taeniopteris 14 4 0 I • Walchians 8 11 0 0 « BrachyphyUtiin 3 0 0 0 Cordaites 10 7 4 15 Callipteridium 1 0 3 2 Caiiiptens s.l. IS 8 0 0 • Neuropleris 5 8 7 22 • Odontopteris 9 7 4 1 Sphenopteris 4 6 3 14 • Dicranophylltim 0 1 0 0 Disdniies 3 0 0 0 * Daubreeia 1 1 0 0 Pecapteris U 5 10 14 Ptychocarpus 0 1 s 4 • Fasdpteris 1 0 0 0 Qadtnia 1 0 0 0 Senftenbergia 0 0 0 3 Ohgocarpia 0 0 3 2 Dicksanites 0 0 4 2 « Protobieckntim 1 0 0 0 CladopMebis 1 0 0 0 Danaeitei 0 1 1 1 Catamites 8 8 10 20 • SphenopKytiu m 9 2 8 15 • Labatann u!a ha 1 0 0 0 Sigiilaria 4 6 3 11 Lepidodendron 0 0 1 13 • Lepidophioios 0 0 0 7 • BatKradendro n 0 0 0 2 Ulodendran 0 0 0 1 Asolanus 0 0 0 3 CaUtstophyton 0 1 0 0 Aletkopteris 0 2 3 16 * Eusphenopteris 1 0 3 9 Neuraiethoptens 0 0 0 2 * Adiaittites 0 0 0 1 Linopteris 0 0 1 7 PENNSYLVANIAN-PERMIAN VEGETATIONAL TRANSITION 813 TABLE 2. Continued, Permian Pry Stephanian Wet StephanucL Taxon (23) on (11) WestpbaLIm Runs Reticidopteris 0 0 0 I Lescuropteris 0 0 0 I Mariopteris: 0 0 0 16 » Eremopieris 0 0 0 3 * Atioiopteris 0 1 0 5 Pseudo mariopteris 0 0 3 0 Karinopteris 0 0 0 2 » Desmapteris 0 0 0 I Paimatopteris 0 0 0 3 Brongniartkes 1 0 0 0 Schizopteris \ 1 0 0 Nemejcopteris 0 2 4 0 Megahpteris 0 0 0 1 Rhadea 0 0 0 Neriapteris 0 0 0 A rcha^opteridium 0 0 0 Tingia 0 0 0 CroiSQpterii 0 0 0 Noeggeratkia 0 0 0 Sphenopteridiam 0 0 0 Xygapteris 0 0 0 1 vician and Cretaceous fossils. Older forms, casionally, as fragmented, allochthonous and hence the communities they comprised, debris transported to basinal wetlands from were progressively displaced of&hore. There, surrounding areas. The fossil record pro- more archaic species, communities, and vides rare glimpses of such floras before they community dynamics persisted. The on- became permanently established in lowland shore-offshore hypothesis embraces more regions. They were contemporaneous with than the origin of new morphologies; it plac- the older lowland floras, but occupied hab- es them within a specific ecological context. itats physically removed from basinal set- The pattern of evolutionary innovation in tings. onshore habitats and conservatism in off- Terminological difficulties encountered shore settings has since been generalized to in describing these edaphically distinct ter- most marine ecosystems of the Phanerozoic restrial areas create conceptual difficulties. (Jablonski and Bottjer, 1983; Sepkoski and Mapes and Gastaldo (1987) hst a myriad of Sheehan, 1983; Sepkoski and Miller, 1985; terms that confuse distinctions between and Bretsky and Klofak, 1985; Bottjer and Ja- among peat swamps and clastic swamps, blonski, 1988), including the Recent (Aron- lowlands and uplands, wetlands and well- son, 1990). The causes of this pattern may drained areas, and basinal and extrabasinal reside in the greater levels of disturbance areas. The most fundamental of these dis- and abiotic stress in near-shore environ- tinctions, in our opinion, is that between ments, creating opportunites for the surviv- wetlands, including their characteristic al of new body plans (Bottjer and Jablonski, swamps, and drier habitats, where plants 1988, and Jablonski and Bottjer, 1990, offer are subject to periodic moisture deficits, a number of alternative driving mecha- particularly under seasonal rainfall regimes. nisms). This is a contrast between mesic settings A similar pattern appears to be wide- (the wetlands), which are relatively homo- spread in vascular plants: groups that ulti- geneous, and moisture-limited environ- mately became numerically abundant in ments, which are physically heterogeneous lowland basinal habitats, where conditions (Havlena, 1970). It is easy to relate and de- for preservation were most favorable, are scribe the characteristics of the wetlands, most often recognized first in settings sug- but difficult to do so for the drier environ- gesting periodic moisture limitation, or, oc- ments. Hence the terminological problems. 814 W. A. DiMICHELE AND R. B. ARONSON The terrestrial analogues of offshore set- given the more limited spectrum of plant tings are poorly drained wetland areas with taxa and biologies. abundant moisture availability that are rarely, if ever, exposed to drought. They are Comparison of Terrestrial and often seen in the fossil record as coastal del- Marine Dynamics taic, coal-bearing rock sequences. These en- Vegetational changes in the late Paleozoic vironments tend to have ecologically per- tropics can be summarized broadly as fol- sistent floras and communities, particularly lows. Many of the plant lineages that came in the Paleozoic (DiMichele and Phillips, to dominate Permian and early Mesozoic 1990). Wetland habitats harbor long-rang- floras first appeared in extrabasinal, dry to ing lineages of phenetically similar species seasonally dry environments. The increase and, most importantly, rarely have been ar- in regional aridity, such as that proposed eas of origin for higher taxa (Knoll, 1984, for the Permian of the southwestern United 1985; DiMichele et al., 1987). The ana- States, is associated with marked increases logues of onshore environments are water- in 1) the number of regional community limited habitats that are, in general, season- types (Read and Mamay, 1964); 2) floristic ally dry and often well-drained. They variation among localities within any one include both basinal centers of sediment ac- community type; and 3) the appearance of cumulation and extrabasinal areas that only many new morphologies. In rare cases (re- rarely and fortuitously preserve plant fos- cently discovered in north-central Texas and sils. It is these environments that fostered not included in this data base) where or- the origin of most ordinal-level taxa of seed ganic-rich deposits occur in earliest Perm- plants and ferns; the poor stratigraphic rec- ian rocks, they retain a "Pennsylvanian" ord of such habitats, at least during the wet- aspect: dominance by pteridosperm taxa ter periods of tropical history, makes as- typical of wetland basinal habitats. A sim- sessment of species turnover and community ilar pattern occurs in Europe and is dis- persistence difficult. Late Paleozoic clades cussed by Broutin et al. (1990). Conifer-rich centered in wetlands, such as sphenopsids floras from dry habitats of Late Pennsyl- and lycopsids (see Bateman et al., 1992), vanian or Early Permian age usually contain show lower morphological disparity than only small numbers and few species from lineages centered in the drier Paleozoic hab- wetland-centered lineages, such as sphenop- itats, such as ferns and seed plants (Crane, terids and certain pecopterids. Figure 2 il- 1985; Doyle and Donoghue, 1986; Roth- lustrates the increased abundance of dry- well, 1987), possibly reflecting differences site habitats and plants in the basinal low- in opportunities for divergence. lands through time. The selective effect of moisture limitation Although the Pennsylvanian-Permian at any one time is completely dependent on strata record only a small segment of the the physiological and structural capabilities history of plant evolution, it is a particularly of the plants existing at that time. Any truly important segment because during this time terrestrial environment may have been a seed-plant dominated, Mesozoic-style eco- moisture-stressed "upland" for early land systems evolved. The first appearance of plants (Beerbower, 1985). Successive lin- conifers, cycads, ginkgoaleans and the cal- eages of plants evolved increased tolerance lipterids in Late Pennsylvanian dry envi- to drought through the Phanerozoic. In ef- ronments, and the later appearance of pel- fect, the adaptive frontier has been pushed tasperms, additional conifer genera, and back through time. Today, there is a much enigmatic groups such as gigantopterids and greater range of vegetation separating the Wattia, in dry habitats of the Early Permian most evolutionarily conservative basinal stand in marked contrast to evolutionary wetlands from the areas of greatest inno- dynamics in the wet lowlands of the Early vation in globally dispersed and highly het- and Middle Pennsylvanian. The time inter- erogeneous moisture-limited areas. We val may be short, but the pattern is re- speculate that the physical length of the gra- markably clear. dient was much shorter in the Paleozoic, Peripheral, moisture-stressed environ- PENNSYLVANIAN-PERMIAN VEGETATIONAL TRANSITION 815 mm ^ ^9^ ^.,n^ WESTPHALIAN Z m STEPHANIAN WOLFCAMPIAN LEONARDIAN m LycopskJ T'^Reriitospie• p Calamiles ^ Coni(«i (SOT^ Qthar The taxa that originated in peripheral, established in the lowlands during the drier habitats in the late Paleozoic tend to Permian. They are mixed with survivors of be subgroups of seed plants. The life his- Carboniferous wetland groups such as tories of seed plants suggest a priiori greater sphenopsids and ferns (Harris, 1926, 1931- extinction resistance than most groups of 1937; Hope and Patterson, 1969; Delevo- lower vascular plants (ferns, lycopsids and ryas and Hope, 1976, 1978, 1981; Up- sphenopsids). This prediction is confirmed church and Doyle, 1981). by the nearly continuous expansion of seed- The terrestrial pattern described here dif- plant diversity during the post-Paleozoic, at fers in several important ways from the pat- the expense of lower vascular plants (Niklas tern in the marine realm, as documented et al., 1985). Thus, as in the marine record, most recently by Jablonski and Bottjer more demanding physical environments (1990). The plant record does not show in- may foster the survival of extinction-resis- dividualistic expansion of clades from pe- tant clades during early stages of diversifi- ripheral, dry environments into the wet cation (Jablonski and Bottjer, 1990; Sep- lowlands. Some taxa, such as conifers, ap- koski, 1991). pear to have moved into the lowlands soon- The evolution of major architectural in- er and in greater numbers than many of the novations (the traditional grounds for rec- broad-leaved species; however, the priority ognition of new higher taxa) in dry, physi- of conifers may be biased taphonomically cally heterogeneous areas, peripheral to by the high preservational potential of de- basinal wetlands, is only half the analogy to cay-resistant conifer foliage. In general, our the onshore-offshore marine pattern. The data and the data discussed by Broutin et other half is the movement of species from al. (1990) suggest that communities from marginal areas into basinal lowlands, and drier habitats behaved as units in replacing their rise to ecological dominance there. Ja- communities from wetter environments. blonski and Bottjer (1990) discounted ex- This whole-community movement does not trinsic environmental factors as causes of appear to be the general condition in the the marine onshore-offshore pattern, and marine environment (Bretsky and KJofak, Sepkoski (1991) argued on theoretical 1985; Bottjer and Jablonski, 1988). grounds that intrinsic evolutionary pro- The spatial relationship of marginal, well- cesses alone could explain the pattern. How- drained, relatively dry areas to basinal wet- ever, Bretsky and KJofak (1985) docu- land areas also differs in a significant way mented onshore-offshore movement in an from the relationship of marine onshore to epicontinental sea contingent on changing offshore habitats. Because successive plant sea level. Uneages were more tolerant of moisture lim- Physical factors appear to have been the itation, the terrestrial "onshore" cannot be driving force in the late Paleozoic terrestri- defined relative to fixed physical reference al-plant shift as well. Marginal taxa ex- points in the sense that the marine onshore panded into basinal habitats in association is defined by the continental margins and with climatic change: increased seasonality coastlines. The abiotic attributes of the of moisture availability in the Euramerican nearshore marine are fixed, in contrast to tropical lowlands during the late Paleozoic the terrestrial environment. The terrestrial (Knoll, 1984; Parrish et al., 1986; Ziegler, lowlands, the "offshore" analogue, are lo- 1990). When more favorable conditions re- cated in coastal areas, near sea level. The turned to the Euramerican tropical lowlands "onshore" analogues represent a heteroge- in the Mesozoic, species of higher taxa that neous association of spatially disjunct and originated in marginal environments were edaphically dissimilar areas. These may vary the ones present in the lowlands to generate from lowland basins in areas with limited the new wetland and swamp lineages. For or highly seasonal rainfall, to true uplands example, Triassic and Early Jurassic coal- distant from areas of major alluvial sedi- bearing rock sequences include conifers, mentation. peltasperms, taeniopterid cycadeoids, cy- Despite some differences, the general pat- cads, and other groups of gymnosperms ei- tern of "onshore" origin, and "offshore" ther belonging to or derived from lineages migration of taxa and the communities they PENNSYLVANIAN-PERMIAN VEGETATIONAL TRANSITION 817 comprise remains a striking parallel be- The nature of the Pennsylvanian-Perm- tween the marine and terrestrial biospheres. ian vegetational change was addressed The terrestrial biosphere was, and may still broadly by White (1933), Florin (1963), be, a more "open" system than the marine Remy (1975), and Havlena (1970) prior to biosphere. Onshore-offshore marine envi- our analysis. Knoll (1984) described it ex- ronments were occupied even in the Cam- plicitly as "replacement." He excluded the brian, though by very different organisms "Paleophytic-Mesophytic" transition from and with a different community structure the strictly competitive mode of floristic than today (Bambach, 1985; Sepkoski and change he envisioned for most of the history Miller, 1985). Opportunities for coloniza- of land plants. The underlying causes of the tion of entirely unoccupied habitats and re- late Paleozoic vegetational transition, spe- sources were much more limited than in the cifically climatic change and associated eco- terrestrial realm. Modem terrestrial envi- logical disruption, occurred at other times ronments may offer the opportunity for during the Phanerozoic as well. It is likely large-scale radiations in desert and polar that more detailed analysis of the plant fos- regions. sil record will reveal additional instances in which radiations or extinctions were caused Proximal Causes of the by changing physical conditions rather than Pennsylva nian-Perm ia n by the superior biologies of the survivors Vegetational TransUion (Valentine et al., 1991). Was this floristic change a displacement or replacement? There has been a growing ACKNOWLEDGMENTS acceptance in paleobotany that plants are We thank R. M. Bateman, R. J. Bumham, fundamentally more "extinction resistant" M. A. Buzas, P. R. Crane, J. B. C. Jackson, than animals, owing to their construction and S. H. Mamay for advice and comments and life history (Knoll, 1984; Traverse, on the manuscript. This is contribution 1988). There are no reported examples of number 5 from the Evolution of Terrestrial global floristic extinction, and supposedly Ecosystems Consortium. no subsequent massive ecological voids into which new or surviving taxa could initiate radiations. Consequently, competition has LCTERATURE CiTED been invoked as the driving force in most ARCHER, A. W., AND C. G. MAPLES. 1987, Analysis plant evolution (Knoll, 1984). In contrast, of binary similarity coffecients: Effects of sample sizes upon distributions. Pataios 2:609-617. opportunity has been implicated as a major ARNOLD, C. A. 1947. An Introduction to Paleobot- driving force in animal evolutionary radi- any. McGraw-Hill, N.Y., USA, ations (Benton, 1987; Jablonski, 1986; Ja- AROKSON, R. B. 1990. Onshore-offsbore patterns of blonski and Bottjer, 1990; Valentine, 1980). human fisbing activity. Palaios 5:88-93. Ecological analysis of the Pennsylvanian- AxELROD, D. I. 1967. Drought, diastropbisttr, and quantum evolution. Evolution 21:201-209. 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00000000000000000000000100010100000000000000100100000000000000000000000000000000 OOOOOOOOOOOOOOOOOOOOOOOOOllOOOlOOOllOOOlOOOOllOllOOOOOOOOOOOOOOOlOOOOOOOOOOOOOOO OOOOOOOOOOOllOOOOOOOOlOlOlOOllllOOlOOOOOOOOllOOlOOOOOOOOOOOOOOOOOOOOOOlOOOOOOOOO 10000000000000000000001101011110000000000000100000000000000000000000010000000000 10000000000000000000001101011000001000000000100000000010000000000000000000000000 00000000000000000000000100000100000000000000000000000000000000000000000000000000 00000000000000000000000000001000001000000000100000000000000000000000000000000000 00000000000000000000000000001110000100001000100000000010001000000000001000000000 OOOOOOOOOOOOOOOOOOOOOOOOOllOllOOOOllOOOOlOOOilOOOOOOOOlOOOOOOOOOlOOOOOlOOOOOOOOO 00000000000000000000000000001000001000001000000000000001000000000000000000000000 OOOOOOOOOOOOOOOOOOOOOOOIOIOOIIOOOOIIOOOOOOOOIOOIOOOOOOIOQOOOOOOOOOOOOOOOOOOOOOOO 00000000000000000000001001001110001100000001110000000010001010010000000100000000 OOOOOOOOOOOOOOOOOOOOOOOOOllOlOlOOOllOOlllOOOllOllHOlOllOOlOOlOlOOll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tamford, TX: Mamay, 1976; Mamay, 1989 FlomiAn^lyz^dar^ Source, <^f Data Lawn TX: Mamay 1976; Mamay. 1975; Mamay, 1986; Mamay, 1988 ^<"'*^- Eddy/Enid, OK: White. 1912 Middle Khuff, Saudi Arabia; Hill and El-Kiiayal, Lake Kemp 2, TX: Mamay, 1967; Mamay. 1986, 1983 Mamay, 1988 Del None TX- Mamay et al, 1984; Mamay et al.. Lake Kemp 1, TX: Mamay, 1966 1988 Hermit Shale, AZ: White, 1929 822 W. A. DiMICHELE AND R. B. ARONSON Emily Irish, TX: Mamay, 1954; Mamay, 1968; Ma- ManningCanyon, UT: Tidwell, 1967; Leary and Pfef- may, 1975; Mamay, 1976; Mamay, 1988 ferkom, 1977 Futda, TX: Mamiay, 1954; Mamay, 1976 Wyoming Hill, lA: Leary, 1981 Perry, OK: Mamay, 1976 Banner, KS: White, 1912; Mamay, 1975; Mamay, LITERATURE SOURCES FOR 1976; Gillespie and PfefFerkorn, 1986 FLORAS ANALYZED Cariton, KS: White, 1912 Unayzah, Saudi Arabia: El-Khayal et al., 1980; El- ARNOLD, C. A. 1941. Some Paleozoic plants from Khayal and Wagner, 1985; Hill et al, 1985 Central Colorado and their stratigraphic signifi- Upper Abo, NM: Ash and Tidwell, 1982 cance. Contrib. Mus. Paleontol. Univ. Michigan 6; Canoncito de la Uva, MM: Hunt, 1983 59-70. Cutler, UT: Mamay and Breed, 1970 ASH, S., AND W. D. TIDWELL 1982, Notes on Upper Reece, KS; White, 1912 Paleozoic plants of central New Mexico, New Mex- Washington, KS: White, 1912 ico Geological Society Guidebook, 33rd Field Con- Spanish Queen, NM: Ash and Tidwell, 1982 ference, Albuqueriiue Country II, pp. 245-248. Padgett, TX: Mamay, 1960 BASSON, P. W. 1968, The fossil flora of the Drywood Geraldine, TX: Sander, 1987 Formation of southwestern Missouri, vol. 44. Uni- Red Tanks, NM: Ash and Tidwell, 1982 versity of Missouri Studies, Columbia, MO USA. Fairplay 1, CO: White, 1912 CANRIGKT, J. E., AND E. B. BLAZEY. 1974. A Lower Fairplay 2, CO: White, 1912 Permian flora from Promontory Butte, central Ar- Moab, LIT: Tidwell, 1988 izona, pp. 57-62. In S. R. Ash (ed.), Guidebook to Promontory Butte, AZ: Cannght and Blazey, 1974 Devonian, Permian and Triassic Plant Localities, Cueli, Spain: Wagner and Martinez Garcia, 1982 East-central Arizona. Paleobotanical Section, Bot. Cooper, TX: USNM Collections Soc. Am., 25th Annual AEBS Meeting. Voyles 1989-11, TX: USNM Collections CRIDLAND, A. A., AND J. E. MORRIS. 1963. Taeniop- Hamilton, KS: Mapes and Rothwell, 1988; Roth well leris, Walchia and Dkhophyllum in the Pennsyl- and Mapes, 1988; Leisman et al., 1988 vanian System of Kansas. Univ. Kans. Sci. Bull. SanTirso, Spain: Wagner and Martinez Garcia, 1982 44:71-85. PuertoUano 1656, Spain: Wagner, 1985 DiMicHELf, W. A, 1982. Fossil plants of shales and PuertoUano 3611, Spain: Wagner, 1985 coals in the Roaring Creek area. In D. L Eggert Swissvale, CO: White, 1912 and T. L. Phillips (eds,). Environments of Depo- Henarejos 3093, Spain: Wagner etal, 1985 sition—Coal Balls, Cuticular Shale and Gray-Shale Kinney, NM: Mamay, 1981; Ash and Tidwell, 1982; Horas in Fountain and Parke Counties, Indiana. Mamay and Mapes, 1992 Indiana, Geol. Surv. Spec. Rept, 30:19-21. Baldwin, KS: Cridland and Morris, 1963 DtMiCHEi^, W. A., AND G. DOLPH. 1981. Compres- Gamett, KS: Wmston, 1983 sion floras of the Upper Mansfield/Lower Brazil McCoy, CO: Read, 1947 and Upper Staunton Formation in Parke and Clay No Business Creek, IL: USNM collections Counties, Indiana. Guidebook to Pennsylvanian Barmelo 384, Spain; Wagner and WinklerPrins, 1983 Plant Localities, AIBS Field Trip No. 2. Indiana Barruelo 118,Spain: Wagner and WinklerPrins, 1985 Univ. Press, Bloomington, IN USA, E and B Coal Company, IL; USNM Collections DIMICHELE, W. A., M. O, RISCKBIETER, D. L. EGGERT, 7-U,0H: McComas, 1988 AND R. A. GASTALDO. 1984. Stem and leaf cuticle Upper Freeport, OH: McComas, 1988 ot Kannoptens: Source of cuticles from the Indiana Mazon Creek, IL: Pfefferkom, 1979 "Paper" Coal. Am. J. Bot, 71:626-637. Galesburg, IL; Pfefferkom, 1979 EL-KHAYAL, A. A., W. G. CHALONER, AND C, R. HILL. Westphalian D, Germany: PfefTerkom, 1979 1980. Paleozoic plants from Saudia Arabia. Nature Chinook, IN: DiMichele and Dolph, 1981 285:33-34. Murphysboro, IL: Read, 1947 EL-KHAYAL, A. A., AND R. H. WAONER. 1985. Upper Tijeras Canyon, NM: Ash and Tidwell, 1982 Permian stratigraphy and megafloras of Saudi Ara- Secor Coal, OK: USNM Collections bia: Palaeogeographic and climatic implications. C. RoweCoal, MO: Basson, 1968 R., 10th Inter. Cong. Carboniferous Strat. Geol. 3: Stanley Cemetary, IN: Wood, 1963 17-26. Cuticle coal, IN: DiMichele and Dolph, 1981; GILLESPIE, W. H., AND H. W. PFEFFERKORN, 1986. DiMichele, 1982; DiMichele et al., 1984 Taeniopterid lamina on Pkasmatocyais megaspo- Roaring Creek, IN; DiMichele and Dolph, 1981; rophylls (Cycadales) from the Lower Permian of DiMichele, 1982 Kansas, U.S.A. Rev. Palaeobot. Palynol. 49:99-116. TarterCoal,IL: Hess etal., 1990; USNM Collections HESS, D., et al. 1990. Floral community variation in Westphalian C, Germany: Pfefferkom, 1979 basal Pennsylvanian strata overlying paleokarst on Sandia Fm, NM; Ash and Tidwell, 1982 mid-Mississippian age St. Louis Limestone, Mc- Jellico, KV: Spurgeon and Jennings, 1985 Clure Quarry, Tennessee, McDonough County, Il- Drury Shale, IL: Read, 1947 linois. North-central Section, Geol. Soc. Am., Ab- stracts with Programs, 22(5):5. Fountain Fm, CO: Jennings, 1980 HILL,C.R.,ANDA.A.EL-KHAYAL. 1983. LatePerm- Evans Peak, CO: Read, 1934 ian plants including Charophytes from the Khuff Arkansas River, CO: Arnold, 1941 Formation of Saudi Arabia. Bull, Br, Mus. (Nat. Forkston Coal, PA: Read, 1946 HisL) (Geol.) 37:105-112. PENNSYLVANIAN-PERMIAN VEGETATIONAL TRANSITION 823 HILL, C. R,, R. H. WAGNER, AND A. A. EL-KHAYAL. Quarry, Manzanita Mountains, New Mexico New 1985. QuasLmia^sn. nov , and early Afar (Papers on the Carboniferous of the Iberian Pen- ous elements. Fine to medium sandstone with mud insula ):171-231. partings above a sequence of red beds and caliches. WAGNER, R. H., AND E. MARTINEZ GARCIA. 1982. No coal. {Wagner and Martinez Garcia, 1982) Description of an Early Permian flora from As- Cooper, Texas: WET-Organic shale/coal within chan- turias and comments on similar occurrences in the nel fill, Underclay and associated soils are non-cal- Iberian Peninsula. Trabaj. Geol., Univ, de Oviedo, careous and evidence locally wet climate and high 12:273-387. water table. {R. W. Hook and W, A, DiMicbele field WAGNER, R. H., J. TALENS, AND B. MELEMDEZ. 1985. obs.; M. Joeckel, University of Iowa, pers. comm., Upper Stephanian stratigraphy and megaflora of 1991) Henarejos (province of Cuenca) in the Cordillera Voyles, 1989-11, Texas: WET-Organic shale/coal Iberica, central Spain. An. Fac. Cienc, Porto, SuppL withm channel fill. Underclay and associated soils Vol. 64 {Papers on the Carboniferous of the Iberian are noncalcareous and evidence locally wet climate Peninsula):445^80. and high water table, (R. W. Hook and W. A. WAGNER,R.H.,ANDC.F.WtNKLERpBiNS. 1983. The DiMicbele field obs.; M, Joeckel, University of Iowa, Cantabrian and Barruehan stratotypes: A summary pers. comm., 199 I) of basin development and biostratigraphic infor- Hamilton Quarry, Kansas: DRY-High relief local land- mation. An. Fac. Ciences, Porto, SuppL 64:359- scape in near coastal setting, suggesting well drained 410. conditions, Channel fill without evidence of coaly, WHCTE, D. 1912. The characters of the fossil plant organic-rich deposits, {Rothwell and Mapes, 1988) Gigamapiem Schenk and its occurrence in North San Tirso, Spain: WET-Dark gray shales and sand- America. Proc. U.S. Nat, Mus. 41:493-516. stones intercallated with pyrodastics. Evidence is . 1929. RoraoftheHermitShale,GrandCan- nondiagnostic but interpretation as "humid" was yon, Arizona, Carnegie Inst. Wash. Pub. 405. based on morphology of plants by Wagner and Mar- WnvsTON, R. B. 1983. A Late Pennsylvanian upland tinez Garcia {1982). flora in Kansas: Systematicsand environmental im- PuertoUano 1656, Spain: WET-Gray shale and sand- plications. Rev. Palaeobot. Palynol. 40:5-31. stone between coal beds. (Wagner, 1985) WooD,J.M. 1963. The Stanley Cemetery Flora {Ear- PuertoUano 3611, Spain: WET-Lacustrine sequence ly Pennsylvanian) of Greene County, Indiana). In- including numerous organic deposits and das tic-rich diana, Geol. Surv. Bull. 29. coals. (Wagner, 1985) ZiDEK, J. 1992. Geology and paleontology of the Kin- Swissvale, Colorado: DRY-Redbeds sequence includ- ney Brick Quarry, Late Pennsylvanian, central New ing numerous limestones. No coal. (White, 1912) Mexico. New Mexico Bur, Mines Min. Res. Bull. Henarejos 3093, Spain: WET-Fluvial-deltaic sequence 138, In press. of coals, limestones and oi^nic shales. (Wagner et al, 1985) Kinney Quarry, New Mexico: DRY-Buffto gray mud- APPENDIX 3 stones and siltstones associated with brackish to ma- rine animals, suggesting a coastal lagoon. No coal. Physical Indicators of Environmental Conditions/or (Zidek, 1992) Late Pennsylvanian Floras Baldwin, Kansas: DRY-Possibly contains some al- Fairplay 2, Colorado (upper beds): DRY-BufTand dark lochthonous elements. Cross-bedded sandstone and gray shales within a redbeds sequence. No coal. shale. No associated coals. Possibly a mixture of (Christopher Durden, Texas Memorial Museum, pers. proximal and distal floodplain elements on poorly comm., 1991)' drained and well drained soils, (Cridlandand Morris, Fairplay 1, Colorado {lower beds): DRY-Sequence 1963) of limestones, including evidence of exposure, such Gamett, Kansas: DRY-Mudflat deposits in the mouth as dessication cracks. No coal. (Christopher Durden, of an estuarine channel cut into limestone bedrock. Texas Memorial Museum, pers. comm., 1991)' Local relief No coal. (Reisz et al., 1982) Moab, Utah: WET-Fluvial-deltaicsediments including McCoy, Colorado: DRY-Non-coal bearing clastic se- coaly shales and sandstones, suggesting locally wet quence. (Read, 1947) Rood-basin conditions. (Tidwell, 1988) No Business Creek, Illinois: WET-Coal underclay and Promontory Butte, Arizona: DRY-Top of channel fill roof shale. (W, A. DiMicbele, field obs.) sequence above organic shale and below calcareous Barruelo 384 and 118, Spain: WET-Deltaic sequence mudstone (soil?) and redbeds, including limestones. that includes numerous thin coals. (Wagner and (Canright and Blazey, 1974) Winkler Prins, 1985) Cueli, Spain: DRY-Possibly contains some allotiion- E and B Coal Company, Illinois: WET-Coal roof shale. (W. A. DiMicbele, field obs,), 7-11 Mine, Ohio: DRY-Complex exposure, Channel fill above "caliche-like" zones su^esting exposure ' The age of these deposits is probably Permian, but and deep weathering. Overall within a coal-bearing because of uncertainty they were included in the anal- sequence, but not a roof shale or in direct association ysis as potentially Stephanian. with coals. {McComas, 1988)