Genetic analysis of populations of the threatened bat <Emphasis Type="Italic">Pteropus mariannus</Emphasis>

The Mariana flying fox (Pteropus mariannus) has suffered substantial decline in recent years. Taxonomic classification of P. mariannus has been inconsistent, with subspecies designations based mainly on geography and morphological variation within small sample sizes. In this study, we examine relationships of P. mariannus across two island groups in the western Pacific Ocean. Microsatellite data and mitochondrial sequences, from D-loop, cytochrome oxidase I, and cytochrome b, suggest that the population on the islands of Palau is genetically isolated from the populations in the Mariana Islands. Our data confirm that the bats of Palau should be considered a separate conservation unit from the bats of the Mariana Islands, supporting the current subspecies separation of these two populations. Our results also suggest that there is gene flow among islands within the Mariana archipelago and that the bats on these islands, currently classified as two subspecies, should be managed as a single conservation unit, although we refrain from suggesting taxonomic revisions until genetic and morphological data become available from geographically intermediate populations.     

Species limits and population differentiation in New Zealand snipes (Scolopacidae: <Emphasis Type="Italic">Coenocorypha</Emphasis>)

At least four species of New Zealand snipes (Coenocorypha) became extinct following the introduction of predatory mammals, and another two species suffered massive range reductions. To investigate species limits and population differentiation in six of the seven remaining offshore populations, we assayed variation in nine microsatellite loci and 1,980 base pairs of four mitochondrial DNA (mtDNA) genes. Genetic diversity in all populations except the largest one on Adams Island in the Auckland Islands was very low in both genomes. Alleles were fixed at many microsatellite loci and for single mtDNA haplotypes, particularly in the populations in the Chathams, Snares, Antipodes and Campbell Islands. Strong population structure has developed, and Chathams and Snares Islands populations are effectively genetically isolated from one another and from the more southern island populations. Based on reciprocal monophyly of lineages and their morphological distinctiveness we recommend that three phylogenetic species should be recognized, C. pusilla in the Chatham Islands, C. huegeli in the Snares Islands and C. aucklandica in the southern islands. The populations of C. aucklandica in the Auckland Islands, Antipodes Island and Campbell Island may warrant recognition as subspecies, and all should be managed as separate conservation units.     

Molecular survey of morphological subspecies reveals new mitochondrial lineages in Podarcis muralis (Squamata: Lacertidae) from the Tuscan Archipelago (Italy)

Recent analyses of molecular markers have significantly revised the traditional taxonomy of Podarcis species (Squamata: Lacertidae), leading to critically reconsider the taxonomic value of several subspecies described only on morphological bases. In fact, lizards often exhibit high morphological plasticity both at the intra‐specific and the intra‐population level, especially on islands, where phenotypic divergences are mainly due to local adaptation, rather than to evolutionary differentiation. The Common wall lizard Podarcis muralis exhibits high morphological variability in biometry, pholidosis values and colour pattern. Molecular analyses have confirmed the key role played by the Italian Peninsula as a multi‐glacial refuge for P. muralis, pointing out the lack of congruence between mitochondrial lineages and the four peninsular subspecies currently recognized. Here, we analyse a portion of the protein‐encoding cytochrome b gene in the seven subspecies described for the Tuscan Archipelago (Italy), in order to test whether the mitochondrial haplotypes match the morphologically based taxonomy proposed for Common wall lizard. We also compare our haplotypes with all the others from the Italian Peninsula to investigate the presence of unique genetic lineages in insular populations. Our results do not agree completely with the subspecific division based on morphology. In particular, the phylogenetic analyses show that at least four subspecies are characterized by very similar haplotypes and fall into the same monophyletic clade, whereas the other three subspecies are closer to peninsular populations from central Italy. From these results, we conclude that at least some subspecies could be better regarded as simple eco‐phenotypes; in addition, we provide an explanation for the distinctiveness of exclusive lineages found in the archipelago, which constituted a refuge for this species during last glacial periods.     

Genetic structure of <Emphasis Type="Italic">Cerasus jamasakura</Emphasis>, a Japanese flowering cherry,revealed by nuclear SSRs: implications for conservation

The genetic resources of a particular species of flowering cherry, Cerasus jamasakura, have high conservation priority because of its cultural, ecological and economic value in Japan. Therefore, the genetic structures of 12 natural populations of C. jamasakura were assessed using ten nuclear SSR loci. The population differentiation was relatively low (F _ST, 0.043), reflecting long-distance dispersal of seeds by animals and historical human activities. However, a neighbor-joining tree derived from the acquired data, spatial analysis of molecular variance and STRUCTURE analysis revealed that the populations could be divided into two groups: one located on Kyusyu Island and one on Honshu Island. Genetic diversity parameters such as allelic richness and gene diversity were significantly lower in the Kyushu group than the Honshu group. Furthermore, STRUCTURE analysis revealed that the two lineages were admixed in the western part of Honshu Island. Thus, although the phylogeographical structure of the species and hybridization dynamics among related species need to be evaluated in detail using several marker systems, the Kyusyu Island and Honshu Island populations should be considered as different conservation units, and the islands should be regarded as distinct seed transfer zones for C. jamasakura, especially when rapid assessments are required.     

The role of western Mediterranean islands in the evolutionary diversification of the spotted flycatcher Muscicapa striata,a long‐distance migratory passerine species

We investigated the evolutionary history of the spotted flycatcher Muscicapa striata, a long distance migratory passerine having a widespread range, using mitochondrial markers and nuclear introns. Our mitochondrial results reveal the existence of one insular lineage restricted to the western Mediterranean islands (Balearics, Corsica, Sardinia) and possibly to the Tyrrhenian coast of Italy that diverged from the mainland lineages around 1 Mya. Mitochondrial genetic distance between insular and mainland lineages is around 3.5%. Limited levels of shared nuclear alleles among insular and mainland populations further support the genetic distinctiveness of insular spotted flycatchers with respect to their mainland counterparts. Moreover, lack of mitochondrial haplotypes sharing between Balearic birds (M. s. balearica) and Corso‐Sardinian birds (M. s. tyrrhenica) suggest the absence of recent matrilineal gene flow between these two insular subspecies. Accordingly, we suggest that insular spotted flycatchers could be treated as one polytypic species (Muscicapa tyrrhenica) that differs from M. striata in morphology, migration, mitochondrial and nuclear DNA and comprises two subspecies (the nominate and M. t. balearica) that diverged recently phenotypically and in mitochondrial DNA and but still share the same nuclear alleles. This study provides an interesting case‐study illustrating the crucial role of western Mediterranean islands in the evolution of a passerine showing high dispersal capabilities. Our genetic results highlight the role of glacial refugia of these islands that allowed initial allopatric divergence of insular populations. We hypothesize that differences in migratory and breeding phenology may prevent any current gene flow between insular and mainland populations of the spotted flycatcher that temporarily share the same insular habitats during the spring migration.     

Genetic relationships of hellbenders in the Ozark highlands of Missouri and conservation implications for the Ozark subspecies (<Emphasis Type="Italic">Cryptobranchus alleganiensis bishopi</Emphasis>)

The hellbender (Cryptobranchus alleganiensis) is an obligately aquatic salamander that is in decline due to habitat loss and disease. Two subspecies of hellbender have been described based on morphological characteristics: C. a. alleganiensis (eastern subspecies) and C. a. bishopi (Ozark hellbender). Current conservation strategies include captive propagation for restorative releases even though information regarding the current levels of genetic variability and structure within populations is not sufficient to effectively plan for conservation of the genetic diversity of the species. To investigate patterns of population structure in the hellbender, we genotyped 276 hellbenders from eight Missouri River drainages, representing both subspecies. Our results showed low levels of within-drainage diversity but strong population structure among rivers, and three distinct genetic clusters. F _ST values ranged from 0.00 to 0.61 and averaged 0.40. Our results confirmed previous reports that C. a. bishopi and C. a. alleganiensis are genetically distinct, but also revealed an equidistant relationship between two groups within C. a. bishopi and all populations of C. a. alleganiensis. Current subspecies delineations do not accurately incorporate genetic structure, and for conservation purposes, these three groups should be considered evolutionarily significant units.     

Integrated species delimitation and conservation implications of an endangered weevil Pachyrhynchus sonani (Coleoptera: Curculionidae) in Green and Orchid Islands of Taiwan

Oceanic islands are productive habitats for generating new species and high endemism, which is primarily due to their geographical isolation, smaller population sizes and local adaptation. However, the short divergence times and subtle morphological or ecological divergence of insular organisms may obscure species identity, so the cryptic endemism on islands may be underestimated. The endangered weevil Pachyrhynchus sonani Kôno (Coleoptera: Curculionidae: Entiminae: Pachyrhynchini) is endemic to Green Island and Orchid Island of the Taiwan‐Luzon Archipelago and displays widespread variation in coloration and host range, thus raising questions regarding its species boundaries and degree of cryptic diversity. We tested the species boundaries of P. sonani using an integrated approach that combined morphological (body size and shape, genital shape, coloration and cuticular scale), genetic (four genes and restriction site‐associated DNA sequencing, RAD‐seq) and ecological (host range and distribution) diversity. The results indicated that all the morphological datasets for male P. sonani, except for the colour spectrum, reveal overlapping but statistically significant differences between islands. In contrast, the morphology of the female P. sonani showed minimum divergence between island populations. The populations of P. sonani on the two islands were significantly different in their host ranges, and the genetic clustering and phylogenies of P. sonani established two valid evolutionary species. Integrated species delimitation combining morphological, molecular and ecological characters supported two distinct species of P. sonani from Green Island and Orchid Island. The Green Island population was described as P. jitanasaius sp.n. Chen & Lin, and it is recommended that its threatened conservation status be recognized. Our findings suggest that the inter‐island speciation of endemic organisms inhabiting both islands may be more common than previously thought, and they highlight the possibility that the cryptic diversity of small oceanic islands may still be largely underestimated.     

Genetic analysis of an endemic archipelagic lizard reveals sympatric cryptic lineages and taxonomic discordance

The importance of genetic data in biodiversity conservation is well established, and knowledge of standing genetic variation within and between populations is important for designing conservation strategies. We investigated partitioning of genetic diversity in an endemic lizard (Leiocephalus psammodromus) distributed in the Turks and Caicos archipelago using mtDNA and AFLP data from 259 individuals sampled across 13 islands. Current taxonomy identifies six or more subspecies of L. psammodromus within the archipelago, several of which have undergone recent drastic reductions in range due to extirpation. However, our results indicate the presence of two independent lineages, one on each of the Turks and Caicos banks, and a third sympatric cryptic lineage on both banks. These lineages do not correspond to current taxonomy and alter our understanding of diversity and conservation of this species. Gross morphological data (mass and snout-vent length) indicate some variation in female size among lineages, indicating the possibility of cryptic morphological variation. Instead of initiating separate conservation measures for nominate subspecies, we recommend a more thorough investigation of the morphology and genetics of this group and a more inclusive conservation program. Our surprising results indicate that other endemic squamates in the Bahamas Archipelago might also exhibit sympatric cryptic diversity that does not correspond to current taxonomic understanding and could have significant impacts on our approach to conservation in this region.     

Delimiting species boundaries for endangered Canary Island grasshoppers based on DNA sequence data

Mitochondrial DNA cytochrome oxidase subunit I and nuclear ITS2 sequences were surveyed from Canary Islands threatened species of the genera Purpuraria and Acrostira (Orthoptera: Pamphagidae). Phylogenetic and population analyses show that the two previously recognized Purpuraria erna subspecies are not valid as conservation units, and that there is a new unrecognized species of Purpuraria, coincident with recently discovered morphological variation within the genus. In addition, mitochondrial introgression seems to occur between the two Purpuraria species in southwest Lanzarote. Species-delimitation based on the morphological taxonomy of Acrostira, which recognizes four single-island endemics, is only partially supported by the genetic data. It shows that currently admitted species from the central and western islands of Tenerife, La Gomera and La Palma are closely related, with evidence of recent gene flow between the Tenerife and La Gomera populations. MtDNA variation also showed that A. euphorbiae, currently considered as the most critically endangered grasshopper species in the Canaries, has lower population diversity than its close relatives.     

Population genetic structure and demography of Magnolia kobus: variety borealis is not supported genetically

Species delimitations by morphological and by genetic markers are not always congruent. Magnolia kobus consists of two morphologically different varieties, kobus and borealis. The latter variety is characterized by larger leaves than the former. For the conservation of M. kobus genetic resources in natural forests, the relationships between morphological and genetic variation should be clarified. We investigated variations in nuclear microsatellites, chloroplast DNA (cpDNA) sequences and leaf morphological traits in 23 populations of M. kobus over the range of species. Two genetically divergent lineages, northern and southern were detected and their geographical boundary was estimated to be at 39°N. The northern lineage consisted of two genetic clusters and a single cpDNA haplotype, while the southern one had multiple genetic clusters and cpDNA haplotypes. The northern lineage showed significantly lower genetic diversity than the southern. Approximate Bayesian computation indicated that the northern and southern lineages had experienced, respectively, population expansion and long-term stable population size. The divergence time between the two lineages was estimated to be 565,000 years ago and no signature of migration between the two lineages after divergence was detected. Ecological niche modeling showed that the potential distribution area in northern Japan at the last glacial maximum was very small. It is thus considered that the two lineages have experienced different population histories over several glacial-inter-glacial cycles. Individuals of populations in the central to northern part of Honshu on the Sea of Japan side and in Hokkaido had large leaf width and area. These leaf characteristics corresponded with those of variety borealis. However, the delimitation of the northern and southern lineages detected by genetic markers (39°N) was not congruent with that detected by leaf morphologies (36°N). It is therefore suggested that variety borealis is not supported genetically and the northern and southern lineages should be considered separately when identifying conservation units based not on morphology but on genetic markers.

     

Multiple origins of invasive and ‘native’ water frogs (Pelophylax spp.) in Switzerland

The marsh frog (Pelophylax ridibundus) has been introduced in many areas in Central and Western Europe as a result of commercial trade with Eastern Europe, and is rapidly replacing the native pool frog (P. lessonae). A large number of Pelophylax species are distributed in Eastern Europe and the strong phenotypic similarity between these species is rendering their identification hazardous. Consequently, alien populations of Pelophylax might not strictly be composed of P. ridibundus as previously suspected. In the present study, we analysed the cytochrome‐b and NADH dehydrogenase subunit 3 genes of introduced and native Pelophylax species from Switzerland (299 individuals) in order to properly identify the source populations of the invaders and the genetic status of the native species. Our study highlighted the occurrence of several genetic lineages of invasive frogs in western Switzerland. Unexpectedly, we also showed that several populations of the native pool frog (P. lessonae) cluster with the Italian pool frog P. bergeri from central Italy (considered by some authors as a subspecies of P. lessonae). Hence, these populations are probably also the result of introductions, meaning that the number of native P. lessonae populations is fewer than expected in Switzerland. These findings have important implications concerning the conservation of the endemic pool frog populations, as the presence of multiple alien species could strongly affect their long‐term subsistence. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 442–449.     

Geometric morphometric and phylogenetic analyses of Arizona Sky Island populations of Scaphinotus petersi Roeschke (Coleoptera: Carabidae)

Scaphinotus petersi Roeschke, 1907 (Carabidae) is a ground beetle endemic to Sky Islands in south‐eastern Arizona. Previous taxonomic studies described several subspecies with morphological differences inhabiting geographically isolated mountain ranges. We combined molecular sequence data and morphometric data, especially head and pronotum shape analyses, to examine the variation and divergence in subspecies and isolated montane populations. In this study, we employ a combination of distance morphometrics as well as geometric morphometrics to quantify the level of morphological variation, and to test the hypothesis that geographically distinct populations of S. petersi are phenotypically distinct. Results suggest that these isolated populations have diverged morphologically and genetically. Phylogenetic analyses identified two monophyletic lineages within the species that correspond generally to pronotum shape. We observed significant morphological variation among most montane populations in of S. petersi, with the pronotum shape as the clearest delimiting trait. © 2015 The Linnean Society of London     

Phylogeography of the blue tit ( Parus teneriffae -group) on the Canary Islands based on mitochondrial DNA sequence data and morphometrics

An analysis of the sequences of the mitochondrial cytochrome b gene (1005 bp) of the Parus teneriffae-group from the Canary Islands and North Africa revealed new insights into the phylogeography of this taxon. The origin of the radiation on the Canarian Archipelago was apparently one of the central islands—Tenerife or Gran Canaria. The populations on El Hierro (P. t. ombriosus) and La Palma (P. t. palmensis) represent distinct monophyletic lineages. Blue tits from Gran Canaria are genetically distinct from those of La Gomera and Tenerife (P. t. teneriffae), which supports the results of other studies and suggests the existence of an—until now—undescribed taxon there. In contrast, the populations on the eastern islands of Fuerteventura and Lanzarote (P. t. degener) could not be distinguished from North African blue tits (P. t. ultramarinus), and these populations should be subsumed under the subspecies ultramarinus. Taxonomic recommendations based on these results include the distinction of the northern European P. caeruleus from P. teneriffae, including blue tits from North Africa and the Canary Islands, the treatment of degener and ultramarinus as synonymous (P. teneriffae ultramarinus) and a new blue tit taxon on the island of Gran Canaria (P. t. hedwigii nov. ssp.), which is formally described. The genetic results are in parts supported by bioacoustic and morphological data.     

A rapid PCR-based diagnostic test for the identification of subspecies of <Emphasis Type="Italic">Acacia saligna</Emphasis>

Subspecific taxa of species complexes can display cryptic morphological variation, and individuals and populations can often be difficult to identify with certainty. However, accurate population identification is required for comprehensive conservation and breeding strategies and for studies of invasiveness and gene flow. Using five informative microsatellite markers and a Bayesian statistical approach, we developed an efficient polymerase chain reaction-based diagnostic tool for the rapid identification of individuals and populations of the Acacia saligna species complex of Western Australia. We genotyped 189 individuals from 14 reference populations previously characterised based on morphology and used these data to investigate population structure in the species complex. High total genetic diversity (H _T = 0.729) and high population differentiation (θ = 0.355) indicated strong intraspecific structuring. With the provision of prior population information, the reference data set was optimally resolved into four clusters, each corresponding to one of the four main proposed subspecies, with very high membership values (Q > 97%). The reference data set was then used to assign individuals and test populations to one of the four subspecies. Assignment was unequivocal for all test individuals from two populations of subsp. lindleyi and for all but one individual of subsp. stolonifera. Individuals from populations of subsp. saligna and subsp. pruinescens showed a degree of genetic affinity for the two subspecies in their assignments, although the majority of individuals were correctly assigned to subspecies. The diagnostic tool will assist in characterising populations of A. saligna, especially naturalised and invasive populations of unknown origin.     

The role of demography and climatic events in shaping the phylogeography of Amazona aestiva (Psittaciformes, Aves) and definition of management units for conservation

Aim The blue‐fronted amazon (Amazona aestiva) is a widely distributed Neotropical parrot with two recognized sub‐species, which are mainly characterized by the colour of the shoulder. We explored mitochondrial DNA variability to determine how demographic processes and historical climatic fluctuations may have contributed to phylogeographical pattern and morphological variation of A. aestiva, and how this information could be useful to understand the evolutionary relationship of this species and the Amazona ochrocephala complex and to determine management units for conservation purposes. Location Brazil and north‐eastern Argentina. Methods We analysed a fragment of COI gene of 78 A. aestiva and 27 A. ochrocephala. We computed a median‐joining network, and the population structure of A. aestiva populations was assessed using a hierarchical analysis of nucleotide diversity. The mismatch distribution, Fu's F_s‐test of neutrality and R² test were used to detect past population expansion. Results All A. aestiva haplotypes and A. ochrocephala subspecies from north‐eastern and southern South America were recovered within the South American clade. Hierarchical analysis of nucleotide diversity of A. aestiva populations detected two geographical groups as obtained by median‐joining network. These two A. aestiva groups showed evidence of a recent population expansion. The time of populations splitting estimated corresponding to the Middle Pleistocene. Main conclusions The two A. aestiva genetic groups identified in our analyses agree with the morphological variation, corresponding to named subspecies. These two A. aestiva groups have undergone a recent population expansion, with low gene flow between them. The expansion of savannah areas may have contributed to the population expansion of these two groups. We concluded that introgression after isolated diversification may better explain haplotype sharing between A. aestiva and A. ochrocephala subspecies. We suggest that management and conservation strategies should consider these two A. aestiva groups (or subspecies) as different management units and should maintain viable populations of these two management units.     

Patterns of morphological evolution in the mandible of the house mouse Mus musculus (Rodentia: Muridae)

The worldwide distributed house mouse, Mus musculus, is subdivided into at least three lineages, Mus musculus musculus, Mus musculus domesticus, and Mus musculus castaneus. The subspecies occur parapatrically in a region considered to be the cradle of the species in Southern Asia (‘central region’), as well as in the rest of the world (‘peripheral region’). The morphological evolution of this species in a phylogeographical context is studied using a landmark‐based approach on mandible morphology of different populations of the three lineages. The morphological variation increases from central to peripheral regions at the population and subspecific levels, confirming a centrifugal sub‐speciation within this species. Furthermore, the outgroup comparison with sister species suggests that M. musculus musculus and populations of all subspecies inhabiting the Iranian plateau have retained a more ancestral mandible morphology, suggesting that this region may represent one of the relevant places of the origin of the species. Mus musculus castaneus, both from central and peripheral regions, is morphologically the most variable and divergent subspecies. Finally, the results obtained in the present study suggest that the independent evolution to commensalism in the three lineages is not accompanied by a convergence detectable on jaw morphology. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 635–647.     

Weak divergence among African, Malagasy and Seychellois hinged terrapins (Pelusios castanoides, P. subniger) and evidence for human-mediated oversea dispersal

Using phylogenetic and haplotype network analyses of 2036 bp of mitochondrial DNA, we compare samples of the two hinged terrapin species Pelusios castanoides and P. subniger from continental Africa, Madagascar and the Seychelles to infer their biogeography. Owing to the long independent history of Madagascar and the Seychelles, the populations from those islands should be deeply divergent from their African conspecifics. Seychellois populations of the two species are currently recognized as Critically Endangered endemic subspecies. However, even though we found within P. subniger evidence for a cryptic species from the Democratic Republic of the Congo, all other samples assigned to this species were undifferentiated. This suggests that Malagasy and Seychellois populations of P. subniger were introduced by humans and that the Seychellois subspecies P. s. parietalis is invalid. This has implications for current conservation strategies for the Critically Endangered Seychellois populations and suggests that measures should rather focus on endemic species. The situation of P. castanoides could be different. Samples from Madagascar and the Seychelles are weakly, but consistently, differentiated from continental African samples, and Malagasy and Seychellois samples are reciprocally monophyletic in maximum likelihood analyses. However, due to a lack of samples from central and northern Mozambique and Tanzania, we cannot exclude that identical continental haplotypes exist there.     

The Postcranial Morphology of Ptilocercus lowii (Scandentia, Tupaiidae): An Analysis of Primatomorphan and Volitantian Characters

The eutherian orders Scandentia, Primates, Dermoptera, and Chiroptera have been grouped together by many morphologists, using various methods and data sets, into the cohort Archonta. Molecular evidence, however, has supported a clade (called Euarchonta) that includes Scandentia, Primates, and Dermoptera, but not Chiroptera. Within Archonta, some systematists have grouped Dermoptera and Chiroptera in Volitantia, while others have grouped Dermoptera and Primates in Primatomorpha. The order Scandentia includes the single family Tupaiidae, with two subfamilies, Ptilocercinae and Tupaiinae. Ptilocercinae is represented only by Ptilocercus lowii, which has been said to be the taxon most closely approximating the ancestral tupaiid. However, most researchers working on archontan phylogeny typically do not treat the order Scandentia as being polymorphic. They usually use Tupaia to represent Scandentia, despite the fact that Ptilocercus is quite distinct from Tupaia and has been argued to be the more plesiomorphic of the two taxa. In this study, a character analysis was performed on postcranial features that have been used to support the competing Primatomorpha and Volitantia hypotheses. In recognition of the polymorphic nature of Scandentia, taxonomic sampling within Scandentia was increased to include Ptilocercus. The postcranium of Ptilocercus was compared to that of tupaiines, euprimates, plesiadapiforms, dermopterans, and chiropterans. Several character states used to support either Primatomorpha or Volitantia, while not found in Tupaia, were found in Ptilocercus. While these features may have evolved independently in Ptilocercus, it is perhaps more likely that they represent features that first evolved in the ancestral archontan and were then lost in one of the extant orders. This character analysis greatly reduces the supportive evidence for the Primatomorpha hypothesis.     

Species of Pleuroxus (Anomopoda,Chydoridae) from the subantarctic islands and southernmost South America: a partial unravelling of the Pleuroxus aduncus problem

Whereas previously all populations of Pleuroxus (now P.) known from the subantarctic islands and southernmost South America were considered to belong to a subspecies of P. aduncus (described from France), now there are five distinct species, only one of which resembles P. aduncus to any significant extent, but even it is a good species. Thus, the taxa are all distinctly different, and none of them could possibly be considered an infraspecies of P. aduncus sens. str. P. macquariensis from Macquarie Island and P. paroplesius and P. varidentatus from South America are new. Of the five species, P. varidentatus resembles P. aduncus most closely, but is separated from it by a number of significant characters. P. wittsteini is presently known from five islands in the south Indian Ocean, but there is considerable uncertainty as to whether all these populations really are the same taxon, because they differ somewhat in the shape of the labrum and in the intensity of sculpturing of the carapace and head. P. scopuliferus from South America is the most distinctive species of the group, having 9 gnathobasic filter setae on trunklimb III instead of the usual 8, a weak ridge on the shell, and a recurved rostrum extending beyond the tip of the labrum. No species of Pleuroxus (or of P., another subgenus of animals formerly assigned simply to Pleuroxus are known from the islands in the Scotia Arc between South America and Antarctica. The patterns of distribution cannot be explained by an on-going passive dispersal of resting eggs. No populations of species on the subantarctic islands are known from any of the southern land masses. Conditions on these islands intuitively must have been more severe during the glacial ages than during the present interglacial, suggesting that any anomopods present were eliminated during the severe glacial periods. Yet, the presence of isolated populations of endemic species on some islands and the complete lack of Pleuroxus on others (e.g. those in the Scotia Arc) argues that conditions, although more severe, still provided opportunities for the maintenance of active populations. Moreover, the morphological differences between populations of P. wittsteini on islands from a few hundred to several thousand kilometers apart likewise argue for genetic isolation over a very long period of time. Deceased