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European Arachnology 2000 (S. Toft & N. Scharff eds.), pp. 303-314. © Aarhus University Press, Aarhus, 2002. ISBN 87 7934 001 6 (Proceedings of the 19th European Colloquium of Arachnology, Århus 17-22 July 2000)

Why no subspecies in ?

OTTO KRAUS Zoologisches Institut und Zoologisches Museum, Universität Hamburg, Martin-Luther-King-Platz 3, D-20146 Hamburg, Germany ([email protected])

Abstract The several tens of thousands of species that have been named so far have almost exclusively proved to be morphospecies; some of them have been tested and proved to be biospecies, but sub- species have only been recognized in a few exceptional instances. This phenomenon cannot be ex- plained by regular speciation mechanisms alone: obviously, these are no different from those ocurring in other groups of the kingdom. However, the species groups that have been sufficiently inves- tigated in spiders indicate that separation fairly quickly produces superspecies composed of allospe- cies (‘semispecies’). The origin of allospecies patterns can be explained by a combination of the regu- lar effects of separation with functional needs to safeguard sperm transfer between sexual partners. Selection pressure towards optimal co-adaptation between male and female copulatory organs may shorten transitory phases at a subspecies level. This could explain the origin of superspecies com- posed of similar but clearly distinguishable biospecies (allospecies); primarily, they are unable to coex- ist sympatrically or even syntopically.

Key words: Arachnida, Araneae, speciation, genital coadaptation, superspecies, allospecies

INTRODUCTION only been named in exceptional instances. It It was Ted Locket who raised the critical ques- may be questionable as to whether such nominal tion of whether some linyphiid spiders from taxa really form subspecies, i.e. subunits of remote localities in really represented polytypic species. The aim of the present contri- true species, as there were only slight morpho- bution is to stimulate discussion by investigating logical character differences on which to base this comparatively unusual situation in more this decision. This was almost 25 years ago on detail. Of course, tradition has played and is the occasion of the 7th International Congress of continuing to play a predominant role, i.e. the Arachnology held in 1977 in Exeter. His prelimi- stabilizing effect of long-established taxonomic nary remarks did not form part of the congress practice. However, the real biological situation volume (see Merrett 1978), but the problem was may not be reflected by practicing conventional of course not forgotten by systematicists, who procedures of this kind. There is accordingly a were interested in the general aspects of speci- real need to try to explain why there is practi- ation and evolutionary biology. However, I am cally no problem in distinguishing morphospe- not aware of any sound discussion later. Not cies from morphospecies without any intermedi- even a hypothesis has been published. So far, ate forms. This aspect is directly linked to modes spider taxonomists have stamped tens of thou- of speciation in spiders. sands of morphospecies, but subspecies have 304 European Arachnology 2000

GENERAL REMARKS ON SPECIES AND ally been distinguished by different authors. SPECIATION Polytypic species seem to occur almost univer- The investigation and subsequent attempts to sally (Rensch 1929). explain this situation will first need some gen- The counterpart - monotypic species - seems eral remarks. to be exceptional. This term designates species without subspecies. They may be geographically Allopatric versus sympatric speciation widely distributed. I refer to the holarctic distri- Allopatric speciation is the predominant mode bution of the araneid Araneus diadematus Clerck, of speciation in . Separation by barriers 1757 (Fig. 1) and similar distribution patterns of causes interruption of genetic exchange between various species of the Erigonidae. Could it be groups of populations; peripheral isolates espe- that species of this kind consist of just one single cially play a major role. Accordingly, interrup- panmictic population? If so, they may be barred tion of the coherent function of gene flow per- from geographic speciation. The same seems to mits divergence (see Mayr 1942, 1963). Sympat- be true for freshwater Bryozoa and various spe- ric speciation, i.e. speciation without geographic cies of the Tardigrada, e.g., Macrobiotus hufelandi isolation, cannot be definitively excluded, but C.A.S. Schultze, 1834 but there is evidence now there is no reason to believe that mechanisms of that this tardigrad species is composite this kind could be of major importance. (Bertolani & Rebecchi 1993). These and other Until now, no sound argument has been put cases have in common the trait that the species forward to contradict this general view. concerned share extraordinary dispersal abili- ties. I refer to ballooning in spiders, to blepharo- Polytypic and monotypic species blasts in freshwater bryozoans and to the dessi- In most sufficiently studied major groups of the cated cryptobiotic states in tardigrades. animal kingdom, many biospecies1 comprise two or more subspecies. As defined by Mayr ANALYSIS (1963), subspecies form an ‘aggregate of local The situation in spiders is heterogeneous. There populations of a species inhabiting a geographic are sedentary species, and in the other extreme, subdivision of the range of the species and dif- others are world champions in ballooning like fering taxonomically from other populations of the Tetragnathidae in the Northern Hemisphere. the species’. Numerous examples are well-docu- Species may have extremely wide holarctic or mented from mammals to birds and from liz- pantropic distribution patterns, such as Neoscona ards to salamanders, etc. This is also true for in- nauticus (L. Koch, 1875). Others are confined to vertebrates such as carabid beetles (Mossakow- relatively small areas (see, for example, Thaler's ski & Weber 1976), and pulmonate gastropods work on alpine species (1994; Thaler et al. 1994)). (Knipper 1939; Mayr & Rosen 1956). See Mayr Almost all these species have in common the (1963) for details and further documentation. fact that they are distinct morphospecies. There According to this definition, the subdivision is practically no variation. This is especially true of polytypic species into subspecies is based on for the taxonomically decisive genital structures. typology. This explains why, in a given species, Examples of the narrow limits for variation of different numbers of subspecies have occasion- such details are presented in Figs. 9-10; they are partly correlated with the occurrence of sepa- 1The present author continues to accept the bio- rated populations (see Kraus & Kraus 1988). In- species concept sensu Mayr (1963) as it is biologi- termediate populations or at least single inter- cal. What is called the phylogenetic species concept mediate specimens between different mor- does not seem to be applicable in the present dis- phospecies are almost unknown in nature2 — cussion: it is based on individuals, not classes, and with the exception of extremely rare teratologi- sets of characters (Goldstein & DeSalle 2000), i.e. cal individuals. There is usually no difficulty in close to typology. Kraus: No subspecies in spiders? 305

Fig. 1. Holarctic distribution of Araneus diadematus and limited distribution of its presumed sister species, A. pallidus (from Grasshoff 1968). assigning even single specimens to morphospe- of the Heptathela and closely related forms cies A, B, or C. (Ryuthela) studied by Haupt (1983) indicates a It is highly improbable that the modes of correlation with their separation on different speciation in spiders could be principally differ- islands (Fig. 2). With respect to only slight differ- ent from those in other animals or at least in ences between material of different origins, other groups of terrestrial . For better Haupt divided H. kimurai (Kishida, 1920) into understanding, three aspects should be consid- the nominate and three further subspecies, and ered:

1. Arguments in favor of regular allopatric speciation mechanisms Various cases are wellknown enough to provide information on speciation events caused by geo- graphical separation. Some selected examples are:

Mesothelae Species differentiation in island representatives

2Hybrids between Tegenaria gigantea Chamberlin & Ivie, 1935 and T. saeva Blackwall, 1844 were found in Yorkshire, England, where both species occur sympatrically (Oxford & Smith 1987; Oxford & Plowman 1991). Only 3% of the sampled male speci- mens were identified as intermediates. They occur occasionally; no hybrid populations were found. Hence, the specific status of the two Tegenaria spe- Fig. 2. Distribution pattern of island representatives cies is not invalidated. There is evidence that two of the genera Heptathela and Ryuthela on southern closely related synanthropic species are expanding Japanese islands. Further differentation into pre- their ranges, perhaps caused by human interference sumed subspecies (H. k. kimurai, k. amamiensis, k. (see Mayr 1963). This case does not seem to be of higoensis, k. yanbaruensis and R. n. nishirai, n. ishigakien- any relevance for the present discussion. sis) not indicated (from Haupt 1983). 306 European Arachnology 2000

Fig. 3. Phylogenetic biogeography of a clade of Hawaiian Tetragnatha species (from Gillespie 1993); (distribution of the widely distributed species T. quasimodo [Hawaii, Maui, Molokai, Lanai, Oahu, Kaui] not indicated).

R. nishihirai Haupt, 1979 [= Heptathela ?] into the web-building behavior totally reduced. Gillespie nominate and one subspecies. Because of the concluded that multiple founder events oc- discontinuous distribution of the species, espe- curred and that speciation required strict geo- cially those occurring on islands, it is hard to graphic isolation; ecological (more than sexual) decide whether these phena form part of two shifts appear to play a role in initiating diver- polytypic species or whether differentiation into gence. In principle, but not exclusively, islands biospecies has already been achieved. were primarily colonized in the sequence of Anyway, the Heptathela case is a convincing their age, i.e., from north to south. Multiple inva- case of allopatric differentiation. sions may have happened, and present distribu- tion patterns indicate cross-colonizations. This Colonization and differentiation in the Hawaiian development parallels the diversification of the Archipelago Hawaiian Drosophilidae into more than 500 spe- In her extensive work on Hawaiian spiders, Gil- cies, approximately 98% of them endemic (for a lespie (e.g. 1993; see also Roderick & Gillespie review see White 1978). 1998) investigated the radiation of certain spider The conclusion is that even tetragnathids can groups, especially tetragnathids. She discovered be subject to complex allopatric speciation events. a fascinating example of differentiation and Their diversity on the Hawaiian islands appar- speciation (Fig. 3). Among others, there is one ently forms a typical case of archipelago speci- clade of cursorial hunters, with the typical ation (Mayr 1963); together with various other Kraus: No subspecies in spiders? 307

Fig. 4. Distribution of species in the western Palaearctic Region (from Kraus & Baur 1974).

examples, it is more spectacular than the thomisid genus Heriaeus of the Western Palae- well-known radiation of Darwin's finches in the arctic. He distinguished three species groups Galapagos archipelago (see also Wagner & Funk and mapped the distribution of 11 species of the 1995). H. hirtus group (Fig. 5). This distribution pattern may be explained by referring to various Atypus species in the western Palaearctic Region well-known glacial refugia. They are currently (Atypidae). designated as Adriato-mediterranean (plus tyr- Three Atypus species occur in the western Palae- rhenian), ponto- mediterranean, Syrian and arctic Region (Kraus & Baur 1974)3. Their differ- Mauretanien faunal elements (see de Lattin entiation is obviously correlated with Pleistocene 1967). They recolonized Central Europe. This is separation into habitats in Western Europe, another example of regular allopatric speciation. southern Siberia, and a southeastern refugium in One could continue, but this would lead to the Balkan region (Fig. 4). Corresponding to these redundancies. The conclusion is that there is no refugia, the recolonization of Central Europe ap- evidence at all for assuming special modes of parently occurred from three directions [for prin- speciation in spiders. But this kind of review ciples of reasoning see de Lattin 1967]. There is no does not provide an answer to the central ques- reason to doubt that the three species originated tion: why were all of the tens of thousands of by allopatric speciation; they prove to be biospe- spider species described almost exclusively as cies as localities are known where they coexist monotypic units? sympatrically; hybrids were never found. 2. Extremely wide distributional areas versus Heriaeus species in the western Palaearctic Region patterns of local species (). As already mentioned, there is a wide spectrum Loerbroks (1983) revised the species of the between holarctic and also pantropic distribu- tional patterns, on the one hand, and considera- bly small areas of occurrence on the other. 3 There is evidence that Atypus muralis Bertkau, 1890 is not different from A. karschi Dönitz, 1887 (see

Kraus & Baur 1974). 308 European Arachnology 2000

Fig. 5. Distribution of species of the Heriaeus hirtus group in the western Palaearctic Region (from Loerbroks 1983).

Geographically wide distributional areas ragnatha shoshone Levi, 1981, then newly discov- It is difficult to explain why certain species were ered in Europe. As the differences on both sides extremely successful in extending their range, of the Atlantic proved to be gradual, not even cosmopolitan areas included. The impression is subspecific rank was assigned. that they form one single panmictic population in certain instances. This can be assumed, e.g. in Geographically limited distributional areas the case of Araneus diadematus, as ballooning spi- Some presently limited distributional areas may derlings may rotate eastwards because of the be relics of formerly wider distributions, but it prevailing wind direction in the Northern Hemi- seems to be much more probable that most of sphere. Grasshoff (1968) stated that specimens of them are the result of speciation events caused A. diadematus from or from North America by complex separations. Glaciations in the Euro- cannot be distinguished from their European pean Alps form a good example (for review see conspecifics. Various ecophenotypes, color vari- de Lattin 1967). There was a complicated pattern ants included, occur repeatedly at different lo- of relatively small ‘Nunatakker’ and also of ma- calities. However, there is no discernible differ- jor refugia (‘massifs de refuge’). This kind of ence at all in the complicated genital structures. fragmentation of previously coherent distribu- Uhl et al. (1992) made a similar observation in tions may well have induced allopatric differen- their study on the North American species Tet- tiations, including speciation. Attempts to link Kraus: No subspecies in spiders? 309 separations in the past (in refugia) of this kind sidered so far in allopatric spider species com- with geographically limited recent distribution plexes. Future work in this direction could be patterns of spiders may — but must not — be promising. speculative. Despite the fact that no reliable method is 3. No transition zones, not even hybrid belts ? known for measuring dispersal ability, spiders The most crucial problem mentioned at the very should not be underestimated. Wunderlich, for beginning of this contribution remains: Until instance, collected thousands of individuals of now, there has been no reliable information on spider species in a limited area in Berlin. Among potential transition zones or at least hybrid belts others, he also found one single male specimen between allopatric phena traditionally classified of the hitherto unknown species Entelecara bero- as morphospecies. The probability is high that linensis (Wunderlich, 1969). As in birds, it could intermediates of this kind do not exist at all (but well be that this was nothing other than an acci- see footnote 2). Genital differences may be min- dential occurrence - as a result of dispersal abil- ute, but they are always distinct in such allo- ity and different from the existence of an estab- patric forms, including presumably isolated lished reproducing population. The same is true populations. This is true for Mediterranean spe- for the discovery of one single female of Araneus cies of the genus Amaurobius, for representatives grossus (C.L. Koch, 1847) in south-western Ger- of the linyphiid genera Lepthyphantes (see Thaler many. The species was reported by Wiehle 1994) and Agyneta (see Tanasevitch 1999), but (1963) as ‘new’ for Germany; but until now, no also for Theridion (Theridiidae) and Acantholycosa further specimen has been found. This demon- (Lycosidae) morphospecies (Thaler, in litt.). strates that occurrence due to dispersal ability should be distinguished from the existence of HYPOTHESIS firmly established, reproducing populations. The present analysis demonstrates normality: The conclusion is that the extension of distri- Compared with other higher animal taxa, modes butional areas does not depend on dispersal of speciation in spiders, as well as available bio- ability alone. Abiotic factors (such as climatic geographical data, do not offer any exclusive conditions), narrow specialization in biological features. However, there is no pecularity dis- properties, the ability to form an ecological niche cernible that could explain the traditional mor- within the framework of complex interdepend- phospecies by morphospecies situation in spi- encies (including competition with other, al- ders. Are there still other, different aspects that ready well-established species) may effectively should be taken into consideration? prevent the extension of geographically limited distributions. Situations cannot be excluded in Application of the superspecies concept which closely related species occur allopatri- Superspecies patterns cally, as they lack sufficient mutual differentia- I would like to refer to the superspecies concept tion. This may explain why allopatry in species first proposed by Mayr (1931). The definition with limited distributions could be obligatory. given by Mayr & Ashlock (1991: 430) reads as Similar situations of mutual exclusion have follows: ‘A monophyletic group of closely re- already been found in other animal groups, in- lated and entirely or largely allopatric species cluding even mammals. As an example, I refer that are too distinct to be included in a single to species of the coccinellid beetle genus Chilo- species or that demonstrate their reproductive corus with obligatory allopatric species com- isolation in a zone of contact.’ This corresponds plexes, both in North America and in the Palae- exactly to the situation in very similar but allo- arctic (see White 1978 for review and other patric morphospecies in spiders. The subunits of cases). There are differences in the karyotypes, superspecies were called ‘semispecies’. This but this aspect does not seem to have been con- term could be misleading, as one could conclude 310 European Arachnology 2000

Fig. 6. Distribution of species of the Lepthyphantes mansuetus group [=Mansuphantes Saaristo & Tanasevitch, 1996] in the European Alps; arrow indicates syntopic occur- rence (from Thaler 1994).

Fig. 7. Distribution of species of the Lepthyphantes annulatus group [=Incestophantes Tanasevitch, 1992] in the western Palaeartic Region (from Thaler et al. 1994).

Fig. 8. Distribution of the Palaearctic species of the Agyneta similis group (from Tanasevitch 1999). Kraus: No subspecies in spiders? 311 that full biospecies rank has not yet been achieved. Thus, Amadon (1967) replaced ‘semispecies’ by introducing the more appropri- ate term ‘allospecies’. It seems to be easy to group a lot of spider phena — currently classified as morphospe- cies — in complexes of superspecies. The im- pression is that polytypic species structures (with a certain number of more or less intergrad- ing subspecies) are replaced by superspecies, with allospecies as subunits. Well-documented examples are already known. One could refer to the already mentioned Heriaeus hirtus complex (Loerbroks 1983) in thomisids (Fig. 5). The linyphiid species Lepthy- phantes mansuetus (Thorell, 1875) and its relatives (Fig. 6) were recently studied by Thaler (1994). Thaler et al. (1994) investigated the complex around L. annulatus (Kulczynski, 1882) (Fig. 7). Similar results were obtained by Tanasevitch (1999) who investigated Agyneta species (Fig. 8). Fig. 9. Intraspecific variation of vulvae of Stegodyphus Thaler and also Tanasevitch had already used dufouri specimens from different localities in northern the appropriate term ‘superspecies’. That the Africa, Aden, the Sudan, Mali and Niger (from Kraus subunits had already achieved full biospecies & Kraus 1988). level was confirmed in at least one case: a local- ity is known where the otherwise allopatric spe- cies L. mansuetus and L. aridus (Thorell, 1875) were found to occur sympatrically; there was not even a single intermediate individual (see Fig. 6, arrow).

Why superspecies with allospecies as subunits? Pure application of the superspecies concept is primarily a matter of correct terminology and should not be misunderstood as an explanation of the biological background. But genital structures and what was formerly called the ‘lock-and-key principle’ (Dufour 1844) may provide the key for a biological interpretation of the origin of al- lospecies patterns. Two aspects should be con- sidered: a) It is generally supposed that complex genital structures in terrestrial arthropods are extremely sensitive in reflecting genetic differ- Fig. 10. Intraspecific variation of terminal lamellae of ences (see e.g. Arnqvist 1997), and b) the need male bulbi of Stegodyphus mimosarum specimens from for an optimal co-adaptation between male and the Congo (a), the Serengeti (b), Durban (c), Natal female copulatory organs. Both factors are inter- (d), the Kruger Park (e), the Transkei coast (f), and linked. As already explained, there are many (g) (from Kraus & Kraus 1988). 312 European Arachnology 2000

Fig. 11. Hypothesis: Diagram illus- trating the possible origin of al- lospecies, including the potential ability to coexist with similar spe- cies at later stages of evolutionary divergence.

examples of comparatively slight but regionally pling mechanisms simply seems to safeguard invariable genital differences. This is not only sperm transfer (Kraus 1968), in some instances true for species complexes in spiders, but has by more than one copulating male (see Wiehle also been found in the Lepidoptera and in many 1967). It is this requirement that apparently sta- other groups, carabid beetles in- bilizes details of copulatory organs. Loerbroks cluded (for review, see de Lattin 1967). Optimal (1983) demonstrated that limited variability may coadaptation has been extensively discussed by be observed in the epigynes but not in the vul- Eberhard (1985). He believes in selection by fe- vae of certain thomisid spiders. Similar variation male choice (see Arnqvist 1997). However, in was observed by Kraus & Kraus (1988) in female spiders female choice may be highly dangerous specimens of African Eresidae, especially in Ste- for males and could probably cause unbalanced godyphus dufouri (Audouin, 1826) (Fig. 9), and in sex ratios. Hence, any selective advantage of the male terminal lamella (Fig. 10) of S. mimosa- female choice seems to be doubtful; it was ap- rum Pavesi, 1883. This kind of slight variability parently not found to occur in nature. Further- remains within narrow limits and does not seem more, male bulbs are not innervated at all, and to influence perfect function. corresponding (tactile) receptors remain to be The hypothesis deduced is as follows: The discovered in sclerotized female copulatory or- main function of coupling mechanisms is to gans. safeguard sperm transfer. Almost perfect homo- Instead, the function of complicated cou- geneity of the functioning components of both Kraus: No subspecies in spiders? 313 male and female genitalia is of high selective REFERENCES advantage. Less perfect mutual adaptation is Amadon, D. 1967. The superspecies concept. regarded as counterproductive. Selection pres- Systematic Zoology 15, 245-249. sure favors uniformity and obliterates devia- Arnqvist, G. 1997. The evolution of animal geni- tions. Two mechanisms may shorten transitory talia: distinguishing between hypotheses by phases at a subspecies level and hence accelerate single species studies. Biological Journal of the the formation of distinct allospecies: Linnean Society 60, 365-379. —the expression of genetic differences in genital Bertolani, R.B. & Rebecchi, L. 1993. A revision of structures in geographically separated popula- the Macrobiotus hufelandi group (Tardigrada, tions (or in separated groups of intercommu- Macrobiotidae), with some observations on nicating populations, respectively), and the taxonomic characters of eutardigrades. —selection pressure towards optimal co- Zoologica Scripta 22 (2), 127-152. adaptation of male and female copulatory or- Dufour, L. 1844. Anatomie générale des Dip- gans within such units, i.e. the origin of obliga- tères. Annales des Sciences naturelles 1, 24-264. tory allopatric biospecies (Fig. 11). Eberhard, W.G. 1985. Sexual selection and animal All progressive transitions — from allospe- genitalia. Harvard Univ. Press, Cambridge. cies to regular species — can be expected when Gillespie, R.G. 1993. Biogeographic patterns of the efficiency of primarily unsolved problems of phylogeny in a clade of endemic Hawaiian coexistence becomes increasingly reduced by the spiders (Araneae, Tetragnathidae). Memoirs acquisition of diverging biological properties. of the Queensland Museum 33 (2), 519-526. An alternative hypothesis would be most Goldstein, P.Z. & DeSalle, R. 2000. Phylogenetic welcome, but I am presently not aware of an- species, nested hierarchies, and character other conceivable model. One possible way of fixation. Cladistics 16 (4), 364-384. testing the hypothesis presented here would be Grasshoff, M. 1968. Morphologische Kriterien to investigate whether there could be any corre- als Ausdruck von Artgrenzen bei Radnetz- lation between the occurrence of allospecies in spinnen der Subfamilie Araneinae (Arach- spiders and the presence of coadapted complex, nida: Araneae: Araneidae). Abhandlungen der instead of comparatively simple, genital struc- senckenbergischen naturforschenden Gesellschaft tures. 516, 1-100. Haupt, J. 1983. Vergleichende Morphologie der PERSPECTIVES AND FUTURE QUESTIONS Genitalorgane und Phylogenie der liphistio- 1. Zones of contact between allospecies should morphen Webspinnen (Araneae: Mesothe- be studied. lae), I. Revision der bisher bekannten Arten. 2. As chromosomal differences between allospe- Zeitschrift für zoologische Systematik und Evolu- cies have been observed in many other animal tionsforschung 21 (4), 275-293. taxa, future studies should include appropriate Knipper, H. 1939. Systematische, anatomische analyses; in spiders, the present information is und tiergeographische Studien an südost- close to zero (for details see e.g. White 1978). europäischen Heliciden (Moll., Pulm.). Ar- 3. The problem of tens of thousands of inde- chiv für Naturgeschichte (NF) 8 (3/4), 327-517. pendently described species without subspecies Kraus, O. 1968. Isolationsmechanismen und can be solved by applying the superspecies con- Genitalstrukturen bei wirbellosen Tieren. cept. Instead of just ‘stamping’ the morphospe- Zoologischer Anzeiger 181 (1-2), 22-38. cies, this approach would lead to a better inte- Kraus, O. & Baur, H. 1974. Die Atypidae der grative understanding of evolutionary and espe- West-Paläarktis. Systematik, Verbreitung cially of biogeographic interdependencies. und Biologie (Arach.: Araneae). Abhandlun- gen und Verhandlungen des naturwissenschaft- lichen Vereins in Hamburg (NF)17, 85-116. 314 European Arachnology 2000

Kraus, O. & Kraus, M. 1988. The genus Stegody- Oxford, G.S. & Plowman, A. 1991. Do large phus (Arachnida, Araneae). Sibling species, house spiders Tegenaria gigantea and T. saeva species groups and parallel origin of social (Araneae, Agelenidae) hybridize in the wild? living. Verhandlungen des naturwissen- A multivariate approach. Bulletin of the Brit- schaftlichen Vereins in Hamburg (NF)30, ish Arachnological Society 8(9), 293-296. 151-254. Rensch, B. 1929. Das Prinzip geographischer Ras- Lattin, G. de 1967. Grundriss der Zoogeographie. G. senkreise und das Problem der Artbildung. Born- Fischer, Jena. träger, Berlin. Loerbroks, A. 1983. Revision der Krabben- Roderick, G.K. & Gillespie, R.G. 1998. Speciation spinnen-Gattung Heriaeus Simon (Arachnida: and phylogeography of Hawaiian terrestrial Araneae: Thomisidae). Verhandlungen des arthropods. Molecular Ecology 7, 519-531. naturwissenschaftlichen Vereins in Hamburg Tanasevitch, A.V. 1999. On some palaearctic spe- (NF)26, 85-139. cies of the spider genus Agyneta Hull, 1911, Mayr, E. 1931. Notes on Halcyon chloris and some with description of four new species (Aranei: of its subspecies. American Museum Novitates Linyphiidae). Arthropoda Selecta 8(3), 201-213. 469, 1-10. Thaler, K. 1994. Vikariante Verbreitung im Mayr, E. 1942. Systematics and the origin of species Artenkreis Lepthyphantes mansuetus in Eu- from the viewpoint of a zoologist. 2nd Ed. Do- ropa und ihre Deutung (Araneae, Liny- ver, New York. phiidae). Entomologia Generalis 18, 171-185. Mayr, E. 1963. Animal Species and Evolution. Thaler, K., van Helsdingen, P. & Deltshev, V. Belknap Press at Harvard Univ. Press, Cam- 1994. Vikariante Verbreitung im Artenkom- bridge. plex von Lepthyphantes annulatus in Europa Mayr, E. & Ashlock, P.D. 1991. Principles of Sys- und ihre Deutung (Araneae, Linyphiidae). tematic Zoology. 2nd Ed. Mc Graw Hill, New Zoologischer Anzeiger 232 (3/4), 111-127. York. Uhl, G., Sacher, P., Weiss, I. & Kraus, O. 1992. Mayr, E. & Rosen, C.B. 1956. Geographic varia- Europäische Vorkommen von Tetragnatha tion and hybridization in populations of Ba- shoshone (Arachnida, Araneae, Tetragna- hama snails (Cerion). American Museum No- thidae). Verhandlungen des naturwissenschaft-- vitates 1806, 1-48. lichen Vereins in Hamburg (NF)33, 247-261. Merret, P. (Ed.) 1978. Arachnology. Seventh Inter- Wagner, W.L. & Funk, V.A. 1995. Hawaiian bio- national Congress. Symposia of the Zoological geography. Smithsonian Series in Compara- Society of London 42. Academic Press, Lon- tive Evolutionary Biology. don. White, M.J.D. 1978. Modes of speciation. Freeman, Mossakowski, D. & Weber, F. 1976. Chromo- San Francisco. somale und morphometrische Divergenzen Wiehle, H. 1963. Beiträge zur Kenntnis der bei Carabus lineatus und C. splendens (Carabi- deutschen Spinnenfauna, III. Zoologische Jahr- dae). Ein Vergleich sympatrischer und allo- bücher (Systematik) 90, 227-298. patrischer Populationen. Zeitschrift für zoolo- Wiehle, H. 1967. Steckengebliebene Emboli in gische Systematik und Evolutionsforschung 14, den Vulven von Spinnen (Arach., Araneae). 280-291. Senckenbergiana Biologica 48 (3), 197-202. Oxford, G.S. & Smith, J.C. 1987. The distribution Wunderlich, J. 1969. Zur Spinnenfauna Deutsch- of Tegenaria gigantea Chamberlin & Ivie, 1935 lands, IX. Beschreibung seltener oder bisher and T. saeva Blackwall, 1844 (Araneae, Age- unbekannter Arten (Arachnida: Araneae). lenidae) in Yorkshire. Bulletin of the British Senckenbergiana Biologica 50 (5/6), 381-393. Arachnological Society 7(4), 123-127.