Genetic Relationships Between Ecologically Divergent Species of Talitrid Amphipod (Crustacea)

MARINE ECOLOGY PROGRESS SERIES Published May 7 Mar Ecol Prog Ser

Genetic relationships between ecologically divergent species of talitrid amphipod (Crustacea)

M. B. Conceiqao*, J. D. D. Bishop", J. P. Thorpe"'

The University of Liverpool, Port Erin Marine Laboratory, Port Erin, Isle of Man, IM9 6JA, United Kingdom

ABSTRACT Allozyme electrophoresis was used to investigate the genetic relationships between several species of the amphipod family Talitridae representative of different ecomorphological groups. The analysis of 21 putative gene loci revealed that in general the species studied have relatively low levels of genetic variability when compared with published data for other crustaceans, including other amphipod species. The genetic identities between the species studied were in general accord with existing taxonomy and in good agreement with the broad relationship expected between taxonomic divergence and genetic identity. Dendrograms produced by UPGMA and Wagner clustering proce- dures differed in the position of 1 species. However, both dendrograms suggested that species of the genera Orchestia (beachfleas) and Talorchestla (sandhoppers) are more closely related to each other than to Tal~trussaltator (also a sandhopper), and hence the results did not show a clear genetic divergence between the different ecological groups of talitrids. The analyses supported the taxonomic deci- sion of previous authors to remove the genus Hyale from the family Talitridae. However, the levels of genetic divergence found within the family are too loiv to reconcile readily with the proposed radiation of the group during the Cretaceous period and indicate that the talitrids probably evolved considerably more recently.

KEY WORDS. Talitrids . Genetics . Allozymes - Amphipods

INTRODUCTION tant source of food intertidally, for instance for the fauna of sandy beaches, while derived nutrients may Talitrid amphipods, along with the larvae of sea- contribute to primary production in nearshore areas weed flies, are the dominant invertebrates of macro- (e.g. Griffiths & Stenton-Dozey 1981, Koop et al. 1982a, phytic detritus (wrack) cast up on the strand line of b). Talitrids are early colonisers of strand debris and both soft and hard shores. These groups accordingly may reach extremely high population densities (e.g. act as the most important macrofaunal consumers of Griffiths & Stenton-Dozey 1981) and levels of produc- cast algae on temperate shores of both the northern tion (Venables 1981). They are exploited by a large and southern hemispheres (e.g. Griffiths & Stenton- range of predators, including fish, birds, mammals and Dozey 1981, Moore & Francis 1985). Talitrids may be other wrack invertebrates (reviewed by Wildish 1988). the predominant consumers of algal floating wrack The family Talitndae exhibits many adaptations for (aevja) (Robertson & Lucas 1983), of Spartina spp, litter semi-terrestrial and terrestrial life, and is unique in saltmarshes (Levinton et al. 1977) and of turtle grass among amphipods in having fully terrestrial represen- debris in the tropics (Venables 1981). Detritus from the tatives (Hurley 1959). In those parts of the world where breakdown of the strand line may constitute an impor- they occur, euterrestrial talitrids (landhoppers) may play a dominant role in the exploitation of land-plant 'Present address: Lab. Bioquimica Marinha, Depto. Qui- debris in forest-floor leaf litter comn~unitieswhich par- mica. Fundagao Universidade do Rio Grande. CP 474. Rio allels that of their maritime counterparts (Bousfield Grande, RS-96201-900, Brazil 1984). "Present address: Manne Biological Association of the UK, The Laboratory, Citadel H111, Plymouth PL1 2PB,UK The Talitridae, with more than 200 described spe- " 'E-mail: [email protected] cies, constitute the largest family within the superfam-

0 Inter-Research 1998 Resale of full artlcle not permitted 226 Mar Ecol Prog Ser 165: 225-233, 1998

11y Talitroidea (Bousfield 1982). Despite advances in taxonomy and many additional distributional records in recent years, major problems remain with the systematics of the group. From distributional data it has been concluded that the Indo-Pacific region of the southern hemisphere is the epicentre of talitroid species diversity (Bousfield 1984). Bousfield proposed that talitrids evolved during the Cretaceous Period and early Cenozoic Era from aquatic ancestors, allied to primitive genera of the family Hyalidae; the break-up of Pangaea into many continents, providing new coastal regions, and the later evolution of angiosperm forests, providing food resources, stimulated the geographical and evolutionary radiation of the talitrids. North Sea Bousfield (1984) also subdivided the family Talitridae into 4 loose systematic-ecological groups: palustral species, which he considered morphologically primitive and which occur in marine, estuarine, and some ireshwaler habitats; beachfleas, which are more advanced species, occur in supralittoral habitats and coastal rain forests, and are non-substrate-modifying; sandhoppers, which are supralittoral substrate-modify- i-g (Surrovcing) species found on sd~idybeaches; and landhoppers, which are specialised terrestrial species occupying forest leaf litter. These commonly used ecomorphological sub-groups of the family are informal and probably polyphyletic (Bousfield 1982, 1984). For instance, within the land- Fig. 1. British Isles: inset shows Isle of Man sampling sites. hoppers Bousfield recognised 2 assemblages, simpli- Site names are given in full in Table 1 dactylate and cuspidactylate forms, with separate evolutionary origins. According to Bousfield (1984) the simplidactylate landhoppers evolved from palustral logeny. The present study investigates genetic rela- ancestors in the southern hemisphere, and the cuspi- tionships between some of the talitrid ecological dactylate landhoppers are thought to be derived from groups defined by Bousfield (1984). To put relation- beachflea ancestors of tropical and warm-temperate ships within the family in context, additional compar- coastal regions. isons are made within the superfamily Talitroidea and Recently some attention has been given to phylo- with one non-talitroid amphipod species. genetic relationships within talitnds, although none of the work has used any molecular techniques. From a cladistic analysis of gammandean morphology Kim & MATERIALS AND METHODS Kim (1993) concluded that the Talitroidea were monophyletic. Lindeman (1991) used phenetic and cladistic Sampling and collecting sites. The landhopper Arci- analysis of morphological data in a phylogenetic study talitrus dorneni was collected amongst leaf litter. All of neotropical landhoppers and Moore et al. (1993) other talitroids and Gammarus cnnicornis were taken used the morphology of the antennary gland exit duct from the intertidal and supralittoral regions of sandy or in an ecological series of talitroids to assess whether rocky shores, and were collected among algae or sand. the differences in form support Bousfield's hypothesis. Samples were maintained alive in the laboratory until The study of enzyme variation has long been used as required for electrophoresis. The species studied and a tool in population genetics and also to provide taxo- the sampling sites (Fig. 1) are listed in Table 1. nomlc information on a wide range of organisms The choice of the 2 non-talitrid species for compar- including many invertebrates (reviewed by, e.g., isons outside the Talitridae followed from previous Thorpe & Sole-Cava 1994; see Stewart 1993 for review work. Thus, an intertidal species of Hyale was used for of amphipod data). The few such studies of talitrids comparison as it is regarded as ecologically analogous (McDonald 1985, 1987, 1991, Bulnheirn & Scholl 1986, and phylogenetically close to the probable ancestor of De Mathaeis et al. 1994) were not concerned with phy- the Talitridae (Bousfield 1984). The genus Hyale has ConceigBo et al.: Genetic relationships between amphipods 227

Table 1. Talitnds and other amphipods used in this study, and the ecological type (for talitrids only; after Bousfield 1984) and sampling locality (see Fig. 1) for each species

Species Ecological type Famlly Sampling site Location

Talitrus salta tor Sandhopper Talitridae Derbyhaven (DBH) Isle of Man (Montagu, 1808) Talorchestia deshayesii Sandhopper Talitridae Castletown Bay, Langness (CSL) Isle of Man (Audouin, 1826) Orchestia gammarellus Beachflea Talitridae Niarbyl (NIB) Isle of Man (Pallas. 1766) Orchestia mediterranea Beachflea Talitridae Calf of Man (CLF) Isle of Man Costa, 1857 Arcitalitrus dorneni Simplidactylate landhopper Talitridae Kylemore Abbey (KLA) Co. Galway, (Hunt, 1925) Ireland Hyale nilssoni - Hyalidae Port Erin Bay (PEB) Isle of Man (Rathke, 1843) Gammarus crinjcornis - Ganlmaridae Rue Point (RUP) Isle of Man Stock, 1966 been used to define the plesiomorphic state for the typical condition of aquatic gammarideans in the com- phylogenetic analyses of talitrid morphological charac- parative study of talitrids by Moore et al. (1993). ters by Bousfield (1984), Lindeman (1991), and Moore Electrophoretic analysis. Electrophoresis followed et al. (1993). It was also taken as the starting point in standard methods (Harris & Hopkinson 1976, Murphy the review of physiological adaptations of talitrids to et al. 1990). The homogenisation buffer used was 0.2 M semi-terrestrial and terrestrial environments by Spicer Tris-HC1 pH 8.0. The homogenates were centrifuged at et al. (1987). The non-talitroid family Ganlmaridae has 3000 X g for 3 min. Full details are given in Conceiqao been considered to include a pool of species represent- (1995). ing the most primitive kind of gammaridean amphipod The buffer systems utilised were (1) Tris-citrate, (Barnard 1974), although this view is by no means uni- pH 8.0 (Sicilian0 & Shaw 1976), (2) discontinuous Tris- versally held (e.g. Bousfield 1984). The well-studied borate-citrate, pH 8.2-8.7 (Poulik 1957), and (3) lithium genus Gammarus has been the subject of many elec- hydroxide, pH 8.15-8.30 (Shaklee & Keenam 1986). trophoretic investigations (see Stewart 1993), and a Thirty-one enzyme systems were tested, of which 13 species of the genus was considered to represent the could be scored in all species (see Table 2). Talitrus saltatorwas used as a standard for the measurement of the relative mobilities of alleles for all species. Table 2. The 13 enzyme systems scored in all species in this The program BIOSYS-1 (Swofford & Selander 1981) study, with E.C. numbers, buffers used, and number of loci studied. See 'Materials and methods, Electrophoretic analy- was used to estimate the variability within species and sis' for numbering of buffer systems genetic differentiation among species. Nei's (1978) unbiased genetic distance was used to construct a Enzyme (abbrev~ation) E.C. Buffer No. of UPGMA phenogram (Sneath & Sokal 1973), and the number system loci Prevosti distance (Wright 1978) was employed to estimate the phylogenetic relationship through the Wag- Acid phosphatase (ACP) 3.1.3.2 2 1 ner procedure (Farris 1972). Aspartate aminotransferase (AAT) 2.6.1.1 2 2 Goodness of fit statistics were chosen as the primary Diaphorase (DIA) 1.8.1.4 2 3 criteria for evaluating which tree-building method pro- Fumarase (FUM) 4.2.1.2 1 1 duced the better tree. The statistics employed were: Glucose-6-phosphate 5.3.1.9 1 1 isomerase (GPI) the f of Farris (1972), the F of Prager & Wilson (1976), Hexokinase (HK) 2.7.1.1 1 1 the percent standard deviation (%SD)of Fitch & Mar- Lactate dehydrogenase (LDH) 1.1.1.27 1 1 goliash (1967), and the cophenetic correlation (CC) of Leucine aminopeptidase (LAP) 3.4.1 1.1 3 2 Sneath & Sokal (1973). These statistics are intended to Malate dehydrogenase (MDH) 1.1.1.37 1 3 estimate the degree to which the output (tree) dis- Malic enzyme (ME) 1.1.1.40 3 2 tances between taxa reflect the corresponding input Mannose-6-phosphate 5.3.1.8 1 1 distances, indicating the amount of homoplasy be- isomerase (MPI) Peptidase (PEP) 3.4.13.11 3 2 tween a pair of taxa (Farris 1972), and are often used to Phosphoglucomutase (PGM) 5.4.2.2 1 1 choose between alternative trees generated by different methods (Swofford 1981). wwmo:~r----W- -+r~aoI I -C +W+-wwwm- mo-md~Zgggo-2: gggoo Agzb ;;g-gmv.omz$ -5 ';1 . m 3 -?h, k Vi C - 0000, ' 000-0- 000000000- 000~0000- 0000000000~ 000000000~ 8888% 88888% 88%88?888% 88888888% C3888g8zg88& $g&g3ggg8g + 0 0 0 0- 00000- OO~OOAOOO~00000000~ r000dONOOO- WO~~OOOOO-

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ooooooro, 000-A proz prop- 00000000~ 0000~ 00000~000000~ 00000~00 e m 888~8888% 0- ooooooooooo ooooooooooooo oooooo 00 c. 88888888- 8888- 0 0 0- 0 0 0 0- 0 0 0 0 0 0 0 m ooooooor, 0000- -00- p-p0= - ppppTz ppp?Op, 000T0- ooooOOOoc- Omroe 82 ooooo OOOOOOA ooooofi Z8 88888888" OWOOO 838% 88gg0 00000N 000000m OOOOOC" 00 '" 0 a A 0- o o 0- 0000- 0- o o o o o oooooov 00000- o o OOOOOrOPz 000-- OOrz 00?PZ 00000000 0000" oo~~~~~~ooooom 888~8888m 00000000- 0 0 0 0- 0 0 0- 0 0 0 0- oooooooo, -000, 0-0- - o o 0, r, WOOOO, 00-000, -0000- r o 40~00000~0000$ 0000$ ~8888b000bb"0000N 00 4 000-000z 0000 000000 OOOOOC 00 t48g84888" 8888- 000 0 0 0 0- 00000- 000000- 0 0 0 0 0 0 0 Conceiqao et a1 : Genetic relationsh~psbetween amphipods 229

Table 3 (continued) Table 4. Mean heterozygosities (H) (SE in parentheses), the mean number of alleles per locus, and percentage of polymorphic loci (P)(0.99 criterion) in the 7 amphipod species Locus, Species studied Alleles 1 2 3 4 5 6 7

HK' Species H Mean no. P (NI (30) (30) (30) (33) Observed Expected alleles 80 0.000 0.000 0.000 0.000 - - 82 0.000 0.000 0.000 0.017 Talitrus 0.020 0.024 85 0.000 0.000 0.000 0.000 saltator (0.014) (0.016) 90 0.000 1.000 1.000 0.983 Talorchestia 0.056 0.047 95 0.000 0.000 0.000 0.000 deshayeui (0.038) (0 032) 100 1.000 0.000 0.000 0.000 Orchestia 0.015 0.016 D1A-l' gammarellus (0.013) (0.014) (NI (30) (30) (30) (33) Orchestia 0.030 0.031 95 0.000 0.000 0.000 0.000 mediterranea (0.016) (0.015) 100 1.000 0.000 0.000 0.000 Arcitahtrus 0.025 0.033 105 0.000 1.000 1.000 1.000 dorrieni (0.017) (0.024) DIA-2 Hyale 0.014 0.013 ' nilssoni (0.01 1) (0.010) (N) (301 (30) (30) (33) 80 0.000 0.000 0.000 0.000 Gan~marus 0.059 0.070 crinicornis (0.027) (0.031) 90 0.000 0.000 0.000 0.000 95 0.000 0.000 0.000 1.000 100 1.000 0.000 0.000 0.000 105 0.000 0.000 1.000 0.000 Table 5. Estimates of Nei's (1978) genetic identity (above the 110 0.000 1.000 0.000 0.000 diagonal) and genetic distance (below the diagonal) between DIA -3 ' the 7 amphipod species. (1) Talitrus saltator, (2) Talorchestia (N) (30) (30) (30) (33) deshayesii, (3) Orchestia gammarellus. (4) Orchestia mediter- 90 0.000 0.000 0.000 0.000 ranea, (5) Arcitalitrus dorrieni, (6) Hyale nilssoni. (7) Gam- 95 0.000 0.000 0 000 1.000 marus crinicornis. 100 1.000 1.000 1 000 0.000 ACP' Species 1 (NI (301 (30) (30) (33) 80 0.000 0.000 0.000 0.000 100 1.000 0.000 0.000 0.000 105 0.000 0.000 1.000 1.000 110 0.000 0.000 0.000 0.000 120 0.000 1.000 0.000 0.000 PEP-1 ' (NI (30) (30) (30) (33) 50 0.000 0.000 0.000 0.000 90 0.000 0.000 0.000 0.076 95 0.000 1.000 0.000 0.000 100 1.000 0.000 1.000 0.924 110 0.000 0.000 0.000 0.000 dorrieni. The remaining loci were monomorphic within species, but were in many cases fixed for alternative PEP-2 ' (NI (30) (30) (30) (33) alleles in different species. 75 0.000 0.000 0.000 0.000 Table 4 summarises the results for mean number of 80 0.000 0.000 0 000 0.000 alleles per locus, percentage of loci polymorphic, and 85 0.000 0.000 0.000 0.000 mean heterozygosity for each species studied. The 95 0.000 0.000 1.000 1.000 100 1.000 1.000 0.000 0.000 observed heterozygosity ranged from 0.014 in Hyale 105 0.000 0.000 0.000 0 000 nilssonl to 0.059 in Gammarus crinicornis. The matrix of genetic similarity and distance coefficients (Nei 1978) is shown in Table 5. The values for genetic iden- All the species were successfully analysed for 13 tity ranged from a very low value of 0.055 between G. enzymes coded by a total of 21 loci. Allele frequencies crinicornis and Arcitalitrus dorrieni to 0.560 between for all species studied are shown in Table 3. Only 4 loci the congeneric species Orchestia gammarellus and 0. (GPI', PGM', MPI', and AAT-1') were consistently mediterranea. polymorphic (0.99 criterion) in several or most of the Both dendrograms (Fig. 2a, b) suggest that Talorch- species. FUM' and PEP-2' were also polymorphic in estia deshayesii, a sandhopper, is more closely related Garnrnarus crinicornis, HI(' and PEP-l' in Orchestia to the beachfleas (Orchestia gammarellus and 0. mediterranea, and LAP-2' and ACP' in Arcitalitrus mediterranea) than to Talitrus saltator, the other sand- 230 Mar Ecol Prog Ser 165: 225-233, 1998

a) GENETICDISTAWCE (NEI. 1978) 2.40 2.00 1.60 1.20 0.80 0.40 0.00 L*I".'''. 1.1

Talirru salrator (sandhoppcr) jralorchcstia deshuyesi~(sandhopper) Orchesria ganmarellus (beachflea) Orchcsria medilerranea(beachflea) Architalirrus dorrieni (landhopper) Hyale nilssoni (marine ~aliuoid) Gammaruscrinicornis (marine gammarid)

Fig. 2. Dendrograms to indicate inter- b) PREVOSTI'SDISTANCE FROlM ROOT relationships of the 7 amphipod 0.00 0.08 0.16 0.24 0.32 0.40 0.48 1.*.1.1.1.1.1 species studied (a) derived by the UPGMA method using Nei's genetic J Talirrus salruror (sandhopper) distance and (b) by the Wagner pro- Architalirrus dorrleni (landhopper) cedure uslng Prevosti's distance. Talorchesfia deshayesii (sandhopper) Goodness of fit statistics: (a) f = 4.312, %SD = = CC = Orcheslia gamrnarellus (beachflea) 14.08. F 12.59, 0.870; (b) f = 0.404, %SD = 4.74, F = 2.46, Orchestia medirerranea (beachflea) CC = 0.969. For further information I ' Hyale nilssoni (marine raliuoid) and references to statistical method- I Gammaruscrinicornis (marinegammarid) ology see 'Materials and methods' hopper species. The main difference between the den- erozygosity was attributable to taxon effects and 41% drogram obtained by the Wagner distance procedure to the effects of protein structure and function. (Fig. 2b) and that obtained by the UPGMA analysis is The landhopper Arcitalitrus dorneni is native to that Arcitalitrus dorrieni was grouped with T. saltator south-east Australia and is thought to have been intro- in the Wagner dendrogram, whereas in the UPGMA duced to the British Isles via imported plants (Richard- dendrogram (Fig. 2a) A. dorneni is the most divergent son 1980). The various isolated colonies of A. dorneni of the talitrid species studied. The goodness of fit sta- in Britain probably arose from relatively few intro- tistics (see Fig. 2a, b) indicate that the Wagner distance duced individuals; hence, a population bottleneck procedure produced the better tree. (founder effect) and consequently reduced levels of allozyme heterozygosity are to be expected. Although the heterozygosities of PGM' and GPI' are relatively DISCUSSION low, the mean level of heterozygosity found for A. dorrieni was similar to that of the native species studied. Levels of genetic variation (A. dorneni was polymorphic for the otherwise monomorphic loci LAP-1' and ACP'.) However, bottlenecks The heterozygosity values for the talitrid species are believed to have a larger effect on allelic diversity studied (Table 4) are low when compared with pub- than on heterozygosity, and if population size in- lished data for several other amphipod species (e.g. creases rapidly following a single bottleneck of short Battaglia et al. 1978, Dickson et al. 1979, Gooch & Het- duration, the loss in mean heterozygosity may be small rick 1979, Siegismund et al. 1985, Kane et al. 1992, (Nei et al. 1975, Leberg 1992). In order to establish Patarnello et al. 1992) and when compared with esti- the significance of the pattern of genetic variation ob- mates for other crustaceans (Hedgecock et al. 1982). served in A, dorrieni, it would be necessary to compare Bulnheim & Scholl (1986) and De Mathaeis et al. (1994) the results with genetic variation of putative ancestral have also reported low levels of genetic variability for Australian populations. Talitrus saltator and Talorchestla deshayesii. Thus lt appears that talitrids may have generally rather low levels of heterozygosity. Levels of heterozygosity vary Genetic relationship between species greatly over the wide range of organisms surveyed (Nevo 1978, Nevo et al. 1984), but the implications of The distribution of genetic identities between the this variation are far from clear (review by e.g. Zouros species studied corresponds with the general relation- & Foltz 1987). Ward et al. (1992) found that for inverte- ship expected between taxonomic divergence and brates about 34 % of variance in average protein het- genetic identity (Thorpe 1982). The genetic identity for Conceiqao et al.: Genetic relatis onships between amphipods 231

the 2 Orchestia species (Table 5) is within the range nis. H. nilssoni was formerly placed in the family Tal- proposed for congeneric species (0.35 to 0.85), and the itridae, but, largely on ecological criteria, has been values of genetic identity among the other different referred to the family Hyalidae within the superfamily genera are around 0.35 or below, also as would be Talitroidea (Bulycheva 1957). This is con~patiblewith predicted. the genetic data presented here. The data also provide However, in a review of genetic data from amphi- limited support for the hypothesis that the talitrids may pods, Stewart (1993) suggested that, when identity val- have originated from aquatic ancestors allied to primi- ues fell between 0.45 and 0.85, it may be difficult to tive hyalids (e.g. Bousfield 1984). make decisions regarding specific status of popula- The degree of genetic divergence reported here tion~,and additional factors such as evidence of a lack between the ecomorphological groups of the Talitridae of gene flow and concordant morphological variation is unexpectedly small in the light of Bousfield's (1984) should be considered. The poor distinction found by evolutionary scenario (see also Hurley 1975), which Stewart is possibly due to a taxonomic effect, since proposed an ancient origin of simplidactylate landhop- most of the data came from the single genus Gam- pers, with a divergence from other groups around 100 marus or other Gammaridae. It appears from the data million years before present, during the Cretaceous summarised by Stewart (1993) that some Garnmarus period. This long divergence is not easily reconciled species are only about as closely related as talitrid with the values of Nei's (1978) genetic identity, which genera. indicate far more recent divergence. Calibrations of Our genetic results do not indicate a clear relation- molecular clocks are controversial and at best inaccu- ship between Bousfield's systematic-ecological groups rate, but our data would generally be considered to of talitrids and their genetic divergence, since both the indicate that the major divergence of the Talitridae has UPGMA and the Wagner procedure dendrograms probably occurred over about the last 10 million years (Fig. 2a, b) suggest that the genera Orchestia (beach- (see Thorpe 1982, 1989, Nei 1987), and thus almost cer- flea) and Talorchestia (sandhopper) are more closely tainly commenced within Neogene (late Cenozoic) related to each other than to Talitrus (sandhopper). times (ca 2 to 24 million yr before present). This differs from the relationship in the phenogram of Overall, therefore, our data, when compared with Bousfield (1982, 1984). However, the relative isolation previous hypotheses, indicate some small but signifi- of Talitrus saltator within the family has also been com- cant differences in patterns of divergence of the Tal- mented on by Hurley (1975) and Moore et al. (1993), itridae, but also show a degree of general agreement, whilst Bousfield (1984) stressed that his groups were although they are not compatible with the very long not necessarily monophyletic. timescale proposed in the major study by Bousfield As outlined above, the genetic relationships among (1984). To clarify further the phylogeny of the talitrids all the species shown by a UPGMA dendrogram using it would be desirable to include some palustral species Nei's genetic distance (Fig 2a) suggest that the land- and cuspidactylate landhoppers in the analysis and hopper Arcitalitrus dorrieni is the most divergent of the also to increase the number of species in each ecologi- talitrid species studied. However, results from the cal group. Wagner procedure, which has stronger statistical support than the UPGMA tree (see Fig. 2a, b), show a dif- Acknowledgements. M.B.C. received financial support from ferent branching pattern for A. dorrieni. In the Wagner the Brasilian Government, through a PhD grant from CAPES, and J.D.D.B. was In rece~ptof an Advanced Research Fellow- dendrogram A. dorrieni was clustered, albeit loosely, ship from the UK Natural Environment Research Council. with Talitrus saltator, suggesting that both species These awards are gratefully acknowledged. share a dlrect common ancestor. It should be noted, however, that none of our results indicates a particu- LITERATURE CITED larly close relationship between A. dorrieni and T. saltator, the type-species of Talitrus, despite the refer- Barnard JL (1974) Evolut~onary patterns in gammal-idean ral of A. dorrieni and other simplidactylate landhop- Amphipoda. Crustaceana 27:137- 146 pers to Talitrus (sensu lato) by some authors (e.g. Hur- Battaglia B. 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Editorial responsibility:Otto Kinne (Editor), Submitted:February 12, 2997; Accepted:November 10, 1997 OldendorfILuhe,Germany Proofsreceived from author(s):April 24, 1998