Territorial behavior in the speckled wood butterflies Pararge xiphia and P. aegeria of Madeira: a mechanism for interspecific competition

Two species of speckled wood butterfly occur in Medeira. Pararge xiphia is endemic and is very similar in morphology, behaviour and general ecology to P. aegeria which was first recorded on the island in 1976. We collected behavioural data on the males of the two species at sites where the indigenous laurel forest meets non-native forest and agriculture. It is in these areas that the two species are found together in particularly high densities. Male Pararge butterflies defend sunlit areas of vegetation and attempt to exclude other butterflies. If a territorial intruder is a conspecific or the other Pararge species, extended chases or spiraling flights may take place. Interactions between the two Pararge species are longer and more likely to be escalated than those between either species and a range of other butterfly species. Pararge aegeria is more aggressive in its territorial behaviour than P. xiphia and the latter may be suffering more from the interactions. The results demonstrate that the two species are competing for space and therefore, that territorial behaviour could be a mechanism by which interspecific competition could be taking place. Any adaptive explanation for the interspecifc territoriality remains speculative but this recent and probably natural, colonization may provide an excellent opportunity to examine the role of interspecific competition in structuring communities. The arrival of P. aegeria on Madeira has created an almost unique natural experiment, the study of which will potentially avoid many of the problems traditionally associated with the study of competition.     

The speckled wood butterflies Pararge xiphia and P. aegeria (Satyridae) on Madeira: distribution, territorial behaviour and possible competition

Madeira is home to two species of speckled wood butterfly. Pararge xiphia is endemic and is common at mid to high altitudes, within and around the edges of the indigenous laurel forest. In 1976 P. aegeria colonized the island and anecdotal reports suggest that it may have been responsible for the loss of P. xiphia from some of its former haunts. The aims of this paper were (1) to provide comprehensive data on the distribution, habitat preferences and recent changes of range of the two species and (2) to examine territorial behaviour to see if inter-specific competition is taking place. Census results show that there are basic differences between the species in altitudinal range and habitat, but they are found together at high densities at habitat boundaries. Repetition of some of the census routes after a 4-year gap suggests that P. aegeria is expanding its range into the areas dominated by P. xiphia. Behavioural data demonstrate that the males may be competing by causing each other to expend more energy in defence of territories. Although competition may be present, it is not yet possible to establish which species is more affected and how competition may have contributed to the recent changes in the species' ranges.     

Species delimitation in the Hwamei Garrulax canorus

Due to the male's elaborate songs, the Hwamei Garrulax canorus is the most popular caged bird in the global Chinese community. Three allopatric Hwamei subspecies have been described: G. c. canorus in central and southern China and northern Indochina, G. c. owstoni from Hainan and G. c. taewanus from Taiwan. We sequenced the entire mitochondrial cytochrome b gene to reconstruct the molecular intraspecific phylogeny of the Hwamei. Molecular phylogenetic trees indicated that individuals of the three subspecies formed three monophyletic clades with high bootstrap support (> 95%). The basal clade was G. c. taewanus . According to a conventional molecular clock (2% divergence per million years), G. c. taewanus split from the other Hwamei taxa around 1.5 million years ago, and G. c. owstoni diverged from G. c. canorus around 0.6 million years ago. Considering the periodic connection between the Asian mainland and nearby continental islands during the glacial periods, habitat vicariance may have played a more important role than geographical vicariance in facilitating the differentiation of these taxa. Molecular diagnosability, population integrity, and concordance between the population ranges and the topology of the phylogenetic tree suggested that the Hwamei should be delimited into at least two full species: G. canorus and G. taewanus . Our work represents one of the first attempts to re-evaluate the intraspecific systematics for an eastern Asian bird species using molecular data.     

Sister species within the Triops cancriformis lineage (Crustacea, Notostraca)

We investigated the phylogenetic relationships among the three presently recognized subspecies of the tadpole shrimp, Triops cancriformis , using mitochondrial 16S and 12S rDNA sequences. Our results indicate that the taxon is divided into two distinct lineages. One lineage is formed of T. c. cancriformis populations and samples from northern Spain that had been classified as T. c. simplex in the most recent literature. The second lineage comprises all populations of T. c. mauritanicus and northern African populations of T. c. simplex . These two main lineages separated 2.3 to 8.9 million years ago, based on the range of inferred molecular clocks recognized for crustacean mtDNA sequence divergence. Percentages of divergence are in the range reported for recognized species in other notostracan lineages and we therefore propose to recognize them as two species, Triops cancriformis and Triops mauritanicus . The latter would comprise two subspecies in northern Africa, one consisting of the Moroccan populations of the former T. c. mauritanicus , the other comprising the African populations of the former T. c. simplex . It also includes three as-yet unnamed lineages. A comparison of morphological characters with the molecular data revealed that the former T. c. simplex cannot be reliably separated from T. c. cancriformis , using morphological characters that have hitherto been used to distinguish among subspecies of T. cancriformis . Our investigation is the first to demonstrate the presence of T. c. cancriformis in Africa (Tunisia). The genetic haplotypes of these populations are identical with haplotypes also occurring in Central and Western Europe, as well as in Sicily. Therefore, we hypothesize that the African populations of T. c. cancriformis represent a result of repeated long-distance dispersal across the Mediterranean Sea.     

Nuclear and mitochondrial phylogeography of the Atlantic forest endemic Xiphorhynchus fuscus (Aves: Dendrocolaptidae): biogeography and systematics implications

We studied the intraspecific evolutionary history of the South American Atlantic forest endemic Xiphorhynchusfuscus (Aves: Dendrocolaptidae) to address questions such as: Was the diversification of this bird's populations associated to areas of avian endemism? Which models of speciation (i.e., refuges, river as barriers or geotectonism) explain the diversification within X. fuscus? Does the genetic data support subspecies as independent evolutionary units (species)? We used mitochondrial (n=34) and nuclear (n=68) DNA sequences of X. fuscus to study temporal and spatial relationships within and between populations. We described four main monophyletic lineages that diverged during the Pleistocene. The subspecies taxonomy did not match all the evolutionary lineages; subspecies atlanticus was the only one that represented a monophyletic and isolated lineage. The distribution of these lineages coincided with some areas of endemism for passerines, suggesting that those areas could be regions of biotic differentiation. The ancestor of X. fuscus diverged approximately 3 million years ago from Amazonian taxa and the phylogeographic pattern suggested that X. fuscus radiated from northeastern Brazil. Neither the riverine nor the geotectonic vicariance models are supported as the primary cause for diversification of geographic lineages, but rainforest contractions and expansions (ecological vicariance) can explain most of the spatial divergence observed in this species. Finally, analyses of gene flow and divergence time estimates suggest that the endangered subspecies atlanticus (from northeastern Brazil) can be considered a full species under the general lineage species concept.     

Life-cycle regulation and life history plasticity in the speckled wood butterfly: are reaction norms predictable?

We investigated whether interpopulational variation in life-cycle regulation and life-history plasticity, in response to photoperiod, is predictable from considerations of what would be the adaptive life cycle and life history in a given environment. The investigation was performed on five populations of the speckled wood butterfly, Pararge aegeria (L.) (Lepidoptera: Nymphalidae), from central and south Sweden, England, Spain and Madeira. Insects from all five populations were reared at all daylengths from 10 h to 20 h at 17^oC. Larval and pupal development times were noted. Predictions were met regarding the type of life-cycle regulation and the shape of reaction norms. Evidence for diapause (larval summer and winter diapause, pupal winter diapause) was found in the three northern populations (P. a. tircis) but not in the two southern populations (P. a. aegeria). Photoperiodic thresholds for diapause induction followed the predicted latitudinal patterns, and this was also the case regarding quantitative regulation of development time (by photoperiod) among directly developing individuals. Under direct development, development time was progressively shorter in shorter daylengms in the two Swedish populations, where this signals progressively later dates. This was not found in the English, Spanish and Madeiran populations where such a response is likely to be maladaptive, because one or more generations of larvae are present before summer solstice. There were also unexpected results, for which we propose preliminary adaptive explanations.     

Phylogeography of the Macaronesian Lettuce Species <Emphasis Type="Italic">Lactuca watsoniana</Emphasis> and <Emphasis Type="Italic">L. palmensis</Emphasis> (Asteraceae)

The phylogenetic relationships and phylogeography of two relatively rare Macaronesian Lactuca species, Lactuca watsoniana (Azores) and L. palmensis (Canary Islands), were, until this date, unclear. Karyological information of the Azorean species was also unknown. For this study, a chromosome count was performed and L. watsoniana showed 2n = 34. A phylogenetic approach was used to clarify the relationships of the Azorean endemic L. watsoniana and the La Palma endemic L. palmensis within the subtribe Lactucinae. Maximum parsimony, Maximum likelihood and Bayesian analysis of a combined molecular dataset (ITS and four chloroplast DNA regions) and molecular clock analyses were performed with the Macaronesian Lactuca species, as well as a TCS haplotype network. The analyses revealed that L. watsoniana and L. palmensis belong to different subclades of the Lactuca clade. Lactuca watsoniana showed a strongly supported phylogenetic relationship with North American species, while L. palmensis was closely related to L. tenerrima and L. inermis, from Europe and Africa. Lactuca watsoniana showed four single-island haplotypes. A divergence time estimation of the Macaronesian lineages was used to examine island colonization pathways. Results obtained with BEAST suggest a divergence of L. palmensis and L. watsoniana clades c. 11 million years ago, L. watsoniana diverged from its North American sister species c. 3.8 million years ago and L. palmensis diverged from its sister L. tenerrima, c. 1.3 million years ago, probably originating from an African ancestral lineage which colonized the Canary Islands. Divergence analyses with *BEAST indicate a more recent divergence of the L. watsoniana crown, c. 0.9 million years ago. In the Azores colonization, in a stepping stone, east-to-west dispersal pattern, associated with geological events might explain the current distribution range of L. watsoniana.     

Speculations on the origins of Plasmodium vivax malaria

It is likely that Plasmodium vivax diverged approximately 2 million years ago from a group of malaria parasites which are now endemic in monkeys and apes in southern Asia. In those times, primates were spread throughout most of Eurasia and Africa, indicating an Old World location, but nothing more precise, for the place of divergence of P. vivax. From approximately 1 million years ago, the Ice Ages would have isolated human malaria, including P. vivax, into humid temperate or warm climate refuges around the Mediterranean, in sub-Saharan Africa and in south and east Asia. As there appears to be no record of humans in south and east Asia from 100,000 to 60,000 years ago, they might not have passed on their parasites, including P. vivax, to modern humans entering the region after this time. Today, all P. vivax might be descended from parasites which infected human populations in the Mediterranean region and in sub-Saharan Africa during the last Ice Age, between 100,000 and 20,000 years ago. Evidence for the latter is provided by the presence of very high frequency RBC Duffy negativity in sub-Saharan Africa.     

Solving cryptogenic histories using host and parasite molecular genetics: the resolution of Littorina littorea's North American origin

Even after decades of investigation using multiple sources of evidence, the natural histories of some species remain unclear (i.e. cryptogenic). A key example is Littorina littorea , the most abundant intertidal snail in northeastern North America. Native to Europe, the snail's ecological history in North America has been debated for over 100 years with no definitive resolution. To resolve its cryptogenic status, we used molecular genetics from a novel combination of the snail and a highly associated trematode parasite, Cryptocotyle lingua . Based on mitochondrial sequences of 370 L. littorea and 196 C. lingua individuals, our results demonstrate a significant reduction in genetic diversity in North America vs. Europe, North American haplotypes nested within European haplotypes, and mean divergence estimates of ~500 years ago from Europe for both host and parasite — thus supporting a recent introduction of both host and parasite to North America from Europe. Our study therefore resolves not only a specific cryptogenic history, but it also demonstrates the success of our approach generally and could be used in resolving difficult invasion histories worldwide.     

Nuclear and mtDNA-based phylogeny of southern African sand lizards, Pedioplanis (Sauria: Lacertidae)

The diversity of lacertid lizards in Africa is highest in the southern African subcontinent, where over two-thirds of the species are endemic. With eleven currently recognized species, Pedioplanis is the most diverse among the southern African genera. In this study we use 2200 nucleotide positions derived from two mitochondrial markers (ND2 and 16S rRNA) and one nuclear gene (RAG-1) to (i) assess the phylogeny of Pedioplanis and (ii) estimate divergence time among lineages using the relaxed molecular clock method. Individual analyses of each gene separately supported different nodes in the phylogeny and the combined analysis yielded more well supported relationships. We present the first, well-resolved gene tree for the genus Pedioplanis and this is largely congruent with a phylogeny derived from morphology. Contrary to previous suggestions Heliobolus/Nucras are sister to Pedioplanis. The genus Pedioplanis is monophyletic, with P. burchelli/P. laticeps forming a clade that is sister to all the remaining congeners. Two distinct geographic lineages can be identified within the widespread P. namaquensis; one occurs in Namibia, while the other occurs in South Africa. The P. undata species complex is monophyletic, but one of its constituent species, P. inornata, is paraphyletic. Relationships among the subspecies of P. lineoocellata are much more complex than previously documented. An isolated population previously assigned to P. l. pulchella is paraphyletic and sister to the three named subspecies. The phylogeny identifies two biogeographical clades that probably diverged during the mid-Miocene, after the development of the Benguella Current. This probably led to habitat changes associated with climate and, in conjunction with physical barriers (Great Escarpment), contributed towards speciation within the genus Pedioplanis.     

Extended phylogeny of Aquilegia: the biogeographical and ecological patterns of two simultaneous but contrasting radiations

Studies of the North American columbines (Aquilegia, Ranunculaceae) have supported the view that adaptive radiations in animal-pollinated plants proceed through pollinator specialisation and floral differentiation. However, although the diversity of pollinators and floral morphology is much lower in Europe and Asia than in North America, the number of columbine species is similar in the three continents. This supports the hypothesis that habitat and pollinator specialisation have contributed differently to the radiation of columbines in different continents. To establish the basic background to test this hypothesis, we expanded the molecular phylogeny of the genus to include a representative set of species from each continent. Our results suggest that the diversity of the genus is the result of two independent events of radiation, one involving Asiatic and North American species and the other involving Asiatic and European species. The ancestors of both lineages probably occupied the mountains of south-central Siberia. North American and European columbines are monophyletic within their respective lineages. The genus originated between 6.18 and 6.57 million years (Myr) ago, with the main pulses of diversification starting around 3 Myr ago both in Europe (1.25–3.96 Myr ago) and North America (1.42–5.01 Myr ago). The type of habitat occupied shifted more often in the Euroasiatic lineage, while pollination vectors shifted more often in the Asiatic-North American lineage. Moreover, while allopatric speciation predominated in the European lineage, sympatric speciation acted in the North American one. In conclusion, the radiation of columbines in Europe and North America involved similar rates of diversification and took place simultaneously and independently. However, the ecological drivers of radiation were different: geographic isolation and shifts in habitat use were more important in Europe while reproductive isolation linked to shifts in pollinator specialisation additionally acted in North America.     

Mitochondrial genomes reveal the global phylogeography and dispersal routes of the migratory locust

The migratory locust, Locusta migratoria, is the most widely distributed grasshopper species in the world. However, its global genetic structure and phylogeographic relationships have not been investigated. In this study, we explored the worldwide genetic structure and phylogeography of the locust populations based on the sequence information of 65 complete mitochondrial genomes and three mitochondrial genes of 263 individuals from 53 sampling sites. Although this locust can migrate over long distances, our results revealed high genetic differentiation among the geographic populations. The populations can be divided into two different lineages: the Northern lineage, which includes individuals from the temperate regions of the Eurasian continent, and the Southern lineage, which includes individuals from Africa, southern Europe, the Arabian region, India, southern China, South‐east Asia and Australia. An analysis of population genetic diversity indicated that the locust species originated from Africa. Ancestral populations likely separated into Northern and Southern lineages 895 000 years ago by vicariance events associated with Pleistocene glaciations. These two lineages evolved in allopatry and occupied their current distributions in the world via distinct southern and northern dispersal routes. Genetic differences, caused by the long‐term independent diversification of the two lineages, along with other factors, such as geographic barriers and temperature limitations, may play important roles in maintaining the present phylogeographic patterns. Our phylogeographic evidence challenged the long‐held view of multiple subspecies in the locust species and tentatively divided it into two subspecies, L. m. migratoria and L. m. migratorioides.     

Phylogeny and biogeography of the carnivorous plant family Sarraceniaceae

The carnivorous plant family Sarraceniaceae comprises three genera of wetland-inhabiting pitcher plants: Darlingtonia in the northwestern United States, Sarracenia in eastern North America, and Heliamphora in northern South America. Hypotheses concerning the biogeographic history leading to this unusual disjunct distribution are controversial, in part because genus- and species-level phylogenies have not been clearly resolved. Here, we present a robust, species-rich phylogeny of Sarraceniaceae based on seven mitochondrial, nuclear, and plastid loci, which we use to illuminate this family's phylogenetic and biogeographic history. The family and genera are monophyletic: Darlingtonia is sister to a clade consisting of Heliamphora+Sarracenia. Within Sarracenia, two clades were strongly supported: one consisting of S. purpurea, its subspecies, and S. rosea; the other consisting of nine species endemic to the southeastern United States. Divergence time estimates revealed that stem group Sarraceniaceae likely originated in South America 44-53 million years ago (Mya) (highest posterior density [HPD] estimate = 47 Mya). By 25-44 (HPD = 35) Mya, crown-group Sarraceniaceae appears to have been widespread across North and South America, and Darlingtonia (western North America) had diverged from Heliamphora+Sarracenia (eastern North America+South America). This disjunction and apparent range contraction is consistent with late Eocene cooling and aridification, which may have severed the continuity of Sarraceniaceae across much of North America. Sarracenia and Heliamphora subsequently diverged in the late Oligocene, 14-32 (HPD = 23) Mya, perhaps when direct overland continuity between North and South America became reduced. Initial diversification of South American Heliamphora began at least 8 Mya, but diversification of Sarracenia was more recent (2-7, HPD = 4 Mya); the bulk of southeastern United States Sarracenia originated co-incident with Pleistocene glaciation, <3 Mya. Overall, these results suggest climatic change at different temporal and spatial scales in part shaped the distribution and diversity of this carnivorous plant clade.     

Phylogeny and biogeography of Crinum L. (Amaryllidaceae) inferred from nuclear and limited plastid non-coding DNA sequences

The genus Crinum L. is the only pantropical genus of the Amaryllidaceae. Phylogenetic and biogeographical analyses of nrDNA ITS and plastid trnL-F sequences for all continental groups of the genus Crinum and related African genera are presented, with the genus Amaryllis used as outgroup. ITS indicates that C. baumii is more closely related to Ammocharis and Cybistetes than to Crinum sensu stricto . Three clades are resolved in Crinum s.s. One unites a monophyletic American group with tropical and North African species. The second includes all southern African species and the Australian endemic C. flaccidum . The third includes monophyletic Madagascar, Australasian and Sino-Himalayan clades, with southern African species. The trnL-F phylogeny resolves an American and an Asian/Madagscar clade, and confirms the relationship of C. flaccidum with species endemic to southern Africa. The salverform, actinomorphic perianths of subg. Crinum appear to have evolved several times in the genus from ancestors with zygomorphic perianths (subg. Codonocrinum ), thus neither subgenus is monophyletic. Biogeographical analyses place the origin of Crinum in southern Africa, as the region is optimized at all ancestral nodes in the tree topology, and in basal interior nodes of all but one of the major clades. The genus underwent three major waves of radiation corresponding to the three main clades resolved in our trees. Two entries into Australia for the genus are indicated, as are separate Sino-Himalayan and Australasian dispersal events.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 349–363.     

The evolution of alternative morphs: density-dependent determination of larval colour dimorphism in a butterfly

Understanding the ultimate causes for the presence of polymorphisms within populations requires knowledge of how the expression of discrete morphs is regulated. In the present study, we explored the determination mechanism of a colour dimorphism in larvae of the butterfly Pararge xiphia (Satyrinae: Nymphalidae) with the ultimate aim of understanding its potential adaptive value. Last-instar larvae of P. xiphia develop into either a green or a brown morph, although all individuals are invariably green during the preceding three instars. A series of laboratory experiments reveal that morph development is strongly environmentally dependent and not the result of alternative alleles at one locus. Photoperiod, temperature, and in particular larval density, all influenced morph determination. The strong effect of a high larval density in inducing the brown morph parallels other known cases of density-dependent melanization in Lepidopteran larvae. Because melanization is often correlated with increased immune function, this type of determination mechanism is expected to be adaptive. However, the ecology and behaviour of P. xiphia larvae suggests that increased camouflage under high-density conditions may be an additional adaptive explanation. We conclude that the colour dimorphism of P. xiphia larvae is determined by a developmental threshold that is influenced both by heredity and by environmental conditions, and that selection for increased immune function and camouflage under high-density conditions may be responsible for maintaining the dimorphism.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 256–266.     

Effect of larval-rearing density on adult life-history traits and developmental stability of the dorsal eyespot pattern in the speckled wood butterfly, Pararge aegeria

Behavioural stresses such as crowding are thought to incur a metabolic cost to insect larvae, and fluctuating asymmetry (FA) has been shown to be a possible indicator of this stress. A study of a Madeiran population of the butterfly Pararge aegeria L. (Lepidoptera: Satyrinae) shows that larval crowding affects larval development and growth, with female larvae being more adversely affected than males. It was predicted that if larval crowding increases FA, male and female P. aegeria adults may show different responses to this stress. The FA of five different wing pattern elements on the dorsal hindwings of adult male and female P. aegeria that had been reared at different larval densities was measured. Crowding in P. aegeria resulted in a trait-specific and sex-specific increase in FA. Although a significant correlation between FA and longevity was not observed, there was a significant correlation with egg-laying rate. Stressed females increased their egg-laying rate. An increased egg-laying rate may carry a further fitness cost through the offspring of stressed females, because high egg-laying rates are associated with a decline in oviposition site quality.     

Colonization history of atlantic island common chaffinches (Fringilla coelebs) revealed by mitochondrial DNA

Common chaffinches (Fringilla coelebs) are thought to have colonized the Atlantic island archipelagoes (the Azores, Madeira, and the Canaries) from neighboring continental populations (Iberia and north Africa) within the last million years. However, colonization may have occurred separately from north Africa to the Canaries and from Iberia to the Azores (as would be predicted geographically) or in one wave from Iberia to the Azores and then to Madeira and the Canaries. These alternatives have different implications for the evolution of morphometric and plumage differentiation in island chaffinches. To determine the most likely colonization route, we estimated the phylogenetic relationships among island and continental subspecies of common chaffinch using sequences from four mtDNA genes (cytochrome b, ATPase 6, NADH 5, and the control region). The most strongly supported mtDNA phylogeny places the continental subspecies together as the sister group to a monophyletic clade containing the island subspecies. This is consistent with a single wave of colonization, and suggests that patterns of similarity among Atlantic island common chaffinches, such as blue pigmentation, short wings, and long tarsi, are due to common colonization history rather than to convergent evolution in a common island environment. However, spectral analysis of phylogenetic splits showed that although monophyly of island haplotypes is favored, there is also substantial support for their polyphyletic origin. We attribute the latter to the confounding effect of homoplasy at multistate sites and to the relatively rapid sequence of colonization events which provided insufficient time for the accumulation of strong phylogenetic signal. These problems are likely to be significant impediments in attempts to test hypotheses of phylogenetic histories of recently evolved populations and taxa.     

Phylogeography of the Ibero-Maghrebian red-eyed grass snake (<Emphasis Type="Italic">Natrix astreptophora</Emphasis>)

We examined phylogeographic differentiation of the red-eyed grass snake (Natrix astreptophora) using 1984 bp of mtDNA and 13 microsatellite loci from specimens collected across its distribution range in southwestern Europe and northwestern Africa. Based on phylogenetic analyses of mtDNA, European N. astreptophora constituted the sister clade to a weakly supported North African clade comprised of two deeply divergent and well-supported clades, one corresponding to Moroccan snakes and the other to snakes from Algeria and Tunisia. This tripartite differentiation was confirmed by analyses of microsatellite loci. According to a fossil-calibrated molecular clock, European and North African N. astreptophora diverged 5.44 million years ago (mya), and the two Maghrebian clades split 4.64 mya. These dates suggest that the radiation of the three clades was initiated by the environmental changes related to the Messinian Salinity Crisis and the reflooding of the Mediterranean Basin. The differentiation of N. astreptophora, with distinct clades in the Iberian Peninsula and in the western and eastern Maghreb, corresponds to a general phylogeographic paradigm and resembles the differentiation found in another co-distributed Natrix species, the viperine snake (N. maura). Despite both species being good swimmers, the Strait of Gibraltar constitutes a significant biogeographic barrier for them. The discovery that North Africa harbours two endemic lineages of N. astreptophora necessitates more conservation efforts for these imperilled snakes.     

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.     

Multiple intercontinental dispersals shaped the distribution area of Hordeum (Poaceae)

The grass genus Hordeum (Poaceae, Triticeae), comprising 31 species distributed in temperate and dry regions of the world, was analysed to determine the relative contributions of vicariance and long-distance dispersal to the extant distribution pattern of the genus. Sequences from three nuclear regions (DMC1, EF-G and ITS) were combined and analysed phylogenetically for all diploid (20 species) and two tetraploid Hordeum species and the outgroup Psathyrostachys. Ages of clades within Hordeum were estimated using a penalized likelihood analysis of sequence divergence. The sequence data resulted in an almost fully resolved phylogenetic tree that allowed the reconstruction of intrageneric migration routes. Hordeum evolved c. 12 million years ago in South-west Asia and spread into Europe and Central Asia. The colonization of the New World and South Africa involved at least six intercontinental exchanges during the last 4 million years (twice Eurasia-North America, North America-South America, twice South America-North America and Europe-South Africa). Repeated long-distance dispersal between the northern and southern hemisphere were important colonization mechanisms in Hordeum.