Camouflaged invasion of Lake Malawi by an Oriental gastropod

In this study we report the first animal invasion, to our knowledge, into Lake Malawi. The colonizer is a non-native morph of the gastropod Melanoides tuberculata that differs substantially in external shell characters from co-occurring indigenous forms. However, because the species possesses extensive within-Africa geographical variation in shell morphology, it was unclear whether the invasion was range expansion of a native African morph, or a colonization from elsewhere. Mitochondrial DNA sequences indicate a southeast Asian origin for the invader, suggesting that shell variation found among indigenous allopatric populations camouflaged an intercontinental invasion.     

The recent evolutionary origin of the phenotypically novel amphipod Hyalella montezuma offers an ecological explanation for morphological stasis in a closely allied species complex

Numerous molecular studies have identified morphologically cryptic, freshwater invertebrate species, but have not suggested possible mechanisms for their phenotypic stasis. The amphipod crustacean genus Hyalella contains numerous morphologically cryptic species in the H. azteca complex, as well as a small number of morphologically very divergent, narrowly endemic taxa. One such taxon, Hyalella montezuma, is the sole planktonic filter-feeder within the North American amphipod fauna, and is known only from Montezuma Well, a fishless travertine spring mound in Arizona, USA. In this study, we conduct a phylogenetic analysis of mtDNA sequence data using likelihood, Bayesian and cladistic approaches to determine both the relationship of H. montezuma to the H. 'azteca' species complex, and to ascertain if its morphological and ecological differentiation have been comparatively recent. The results show that H. montezuma has a very close phylogenetic affiliation with one lineage in the H. azteca complex, indicating that its origin has been recent. We present evidence suggesting that fish predation is an important ecological factor, which constrains morphological and ecological diversification within the genus Hyalella, and that Montezuma Well has provided a relaxation on this constraint.     

DNA barcoding reveals extraordinary cryptic diversity in an amphipod genus: implications for desert spring conservation

DNA barcoding has revealed unrecognized species in several animal groups. In this study we have employed DNA barcoding to examine Hyalella, a taxonomically difficult genus of amphipod crustaceans, from sites in the southern Great Basin of California and Nevada, USA. We assessed the extent of species diversity using a species screening threshold (SST) set at 10 times the average intrapopulation cytochrome c oxidase subunit I (COI) haplotype divergence. Despite the fact that this threshold approach is more conservative in delineating provisional species than the phylogenetic species concept, our analyses revealed extraordinary levels of cryptic diversity and endemism. The SST discriminated two provisional species within Hyalella sandra, and 33 provisional species within Hyalella azteca. COI nucleotide divergences among these provisional species ranged from 4.4% to 29.9%. These results have important implications for the conservation of life in desert springs - habitats that are threatened as a result of groundwater over-exploitation.     

Genetic and morphological diversity of mouse lemurs (Microcebus spp.) in northern Madagascar: The discovery of a putative new species?

Tropical forests harbor extremely high levels of biological diversity and are quickly disappearing. Despite the increasingly recognized high rate of habitat loss, it is expected that new species will be discovered as more effort is put to document tropical biodiversity. Exploring under‐studied regions is particularly urgent if we consider the rapid changes in habitat due to anthropogenic activities. Madagascar is known for its extraordinary biological diversity and endemicity. It is also threatened by habitat loss and fragmentation. It holds more than 100 endemic primate species (lemurs). Among these, Microcebus (mouse lemurs) is one of the more diverse genera. We sampled mouse lemurs from several sites across northern Madagascar, including forests never sampled before. We obtained morphological data from 99 Microcebus individuals; we extracted DNA from tissue samples of 42 individuals and amplified two mitochondrial loci (cytb and cox2) commonly used for species identification. Our findings update the distribution of three species (Microcebus tavaratra, Microcebus arnholdi, and Microcebus mamiratra), including a major increase in the distribution area of M. arnholdi. We also report the discovery of a new Microcebus lineage genetically related to M. arnholdi. Several complementary approaches suggest that the newly identified Microcebus lineage might correspond to a new putative species, to be confirmed or rejected with additional data. In addition, morphological analyses showed (a) clear phenotypic differences between M. tavaratra and M. arnholdi, but no clear differences between the new Microcebus lineage and the sister species M. arnholdi; and (b) a significant correlation between climatic variables and morphology, suggesting a possible relationship between species identity, morphology, and environment. By integrating morphological, climatic, genetic, and spatial data of two northern Microcebus species, we show that the spatial distribution of forest‐dwelling species may be used as a proxy to reconstruct the past spatial changes in forest cover and vegetation type.     

隐种及其在两栖动物中的研究进展

近年来,由于分子生物学的迅猛发展,物种内隐藏的生物多样性越来越多地被发现,由此引发的隐种问题也备受关注。隐种的存在对现有的生物多样性评估提出了挑战。在实践上,隐种的界定对于自然资源的保护和管理具有重要意义。两栖动物由于迁移能力较弱,通常具有较强的遗传分化,因而可能包含较丰富的隐种多样性。简述了隐种的概念和形成机制,归纳了国内外两栖类动物中隐种的研究进展,并着重介绍了界定两栖动物隐种的研究方法,最后,对今后两栖动物隐种的研究作了简要展望。我国两栖动物资源丰富,并具有独特的地形和气候特点,对这些物种遗传多样性和系统地理学的研究亟待开展。     

Diversification and the adaptive radiation of the vangas of Madagascar

The vangas of Madagascar exhibit extreme diversity in morphology and ecology. Recent studies have shown that several other Malagasy species also are part of this endemic radiation, even as the monophyly of the clade remains in question. Using DNA sequences from 13 genes and representatives of all 15 vanga genera, we find strong support for the monophyly of the Malagasy vangids and their inclusion in a family along with six aberrant genera of shrike-like corvoids distributed in Asia and Africa. Biogeographic reconstructions of these lineages include both Asia and Africa as possible dispersal routes to Madagascar. To study patterns of speciation through time, we introduce a method that can accommodate phylogenetically non-random patterns of incomplete taxon sampling in diversification studies. We demonstrate that speciation rates in vangas decreased dramatically through time following the colonization of Madagascar. Foraging strategies of these birds show remarkable congruence with phylogenetic relationships, indicating that adaptations to feeding specializations played a role in the diversification of these birds. Vangas fit the model of an 'adaptive radiation' in that they show an explosive burst of speciation soon after colonization, increased diversification into novel niches and extraordinary ecomorphological diversity.     

Remarkable morphological stasis in an extant vertebrate despite tens of millions of years of divergence

The relationship between genotypic and phenotypic divergence over evolutionary time varies widely, and cases of rapid phenotypic differentiation despite genetic similarity have attracted much attention. Here, we report an extreme case of the reverse pattern--morphological stasis in a tropical fish despite massive genetic divergence. We studied the enigmatic African freshwater butterfly fish (Pantodon buchholzi), whose distinctive morphology earns it recognition as a monotypic family. We sequenced the mitochondrial genome of Pantodon from the Congo basin and nine other osteoglossomorph taxa for comparison with previous mitogenomic profiles of Pantodon from the Niger basin and other related taxa. Pantodon populations form a monophyletic group, yet their mitochondrial coding sequences differ by 15.2 per cent between the Niger and Congo basins. The mitogenomic divergence time between these populations is estimated to be greater than 50 Myr, and deep genetic divergence was confirmed by nuclear sequence data. Among six sister-group comparisons of osteoglossomorphs, Pantodon exhibits the slowest rate of morphological divergence despite a level of genetic differentiation comparable to both species-rich (e.g. Mormyridae) and species-poor (e.g. Osteoglossidae) families. Morphological stasis in these two allopatric lineages of Pantodon offers a living vertebrate model for investigating phenotypic stability over millions of generations in the face of profound fluctuations in environmental conditions.     

Testing concordance in species boundaries using acoustic,morphological, and molecular data in the field cricket genus Itaropsis (Orthoptera: Grylloidea,Gryllidae: Gryllinae)

In most taxa, species boundaries are inferred based on differences in morphology or DNA sequences revealed by taxonomic or phylogenetic analyses. In crickets, acoustic mating signals or calling songs have species‐specific structures and provide a third data set to infer species boundaries. We examined the concordance in species boundaries obtained using acoustic, morphological, and molecular data sets in the field cricket genus Itaropsis. This genus is currently described by only one valid species, Itaropsis tenella, with a broad distribution in western peninsular India and Sri Lanka. Calling songs of males sampled from four sites in peninsular India exhibited significant differences in a number of call features, suggesting the existence of multiple species. Cluster analysis of the acoustic data, molecular phylogenetic analyses, and phylogenetic analyses combining all data sets suggested the existence of three clades. Whatever the differences in calling signals, no full congruence was obtained between all the data sets, even though the resultant lineages were largely concordant with the acoustic clusters. The genus Itaropsis could thus be represented by three morphologically cryptic incipient species in peninsular India; their distributions are congruent with usual patterns of endemism in the Western Ghats, India. Song evolution is analysed through the divergence in syllable period, syllable and call duration, and dominant frequency. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 285–303.     

An integrative approach to the taxonomy of the pigmented European Pseudomonocelis Meixner, 1943 (Platyhelminthes: Proseriata)

Only a few species belonging to the Proseriata (Platyhelminthes) show a parenchymatic pigmentation, which may aid identification. Among these, Pseudomonocelis agilis has a yellowish body and is provided with a reddish–brown girdle in front of the statocyst. The species is known for limited areas of northern Europe and the Mediterranean. The present study was conducted to assess both the taxonomic status of populations attributed to the species across the unusually wide range for an interstitial flatworm, which lacks an obvious means of dispersal, and the levels of genetic variability within and among populations, by employing an integrative approach that included the analyses, on six populations, of three molecular markers (small subunit ribosomal 18S‐like gene, inter‐simple sequence repeat, allozymes), karyotypes, and 11 morphological characters. Furthermore, crossbreeding experiments were carried out on the Mediterranean populations. The results obtained revealed the existence of four highly divergent genotypic clusters, accompanied by karyological differences, with complete intersterility among the clusters tested. The combination of approaches adopted strongly supports the conclusion that the wide‐ranging European pigmented species P. agilis is actually composed of four species: P. agilis in the Baltic area; Pseudomonocelis cetinae in the Adriatic; and Pseudomonocelis sp. nov. A and Pseudomonocelis sp. nov. B in the western and eastern Mediterranean, respectively. The latter two species are morphologically indistinguishable for the parameters essayed. Reconstruction of the phylogenetic relationships of these taxa, including congeneric and consubfamilial outgroups, showed that pigmentation is a plesiomorphic condition for the genus Pseudomonocelis and that Pseudomonocelis sp. nov. A shares a previously undetected, sister‐group relationship with species of the unpigmented P. ophiocephala complex. The present study thus depicts complex speciation processes in a mesopsammic species, which involves allopatric divergence operating on different scales and ecological shifts, and highlights that the contribution of microturbellarians to marine biodiversity may be seriously underestimated. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 907–922.     

Diversification across biomes in a continental lizard radiation

Ecological opportunity is a powerful driver of evolutionary diversification, and predicts rapid lineage and phenotypic diversification following colonization of competitor‐free habitats. Alternatively, topographic or environmental heterogeneity could be key to generating and sustaining diversity. We explore these hypotheses in a widespread lineage of Australian lizards: the Gehyra variegata group. This clade occurs across two biomes: the Australian monsoonal tropics (AMT), where it overlaps a separate, larger bodied clade of Gehyra and is largely restricted to rocks; and in the larger Australian arid zone (AAZ) where it has no congeners and occupies trees and rocks. New phylogenomic data and coalescent analyses of AAZ taxa resolve lineages and their relationships and reveal high diversity in the western AAZ (Pilbara region). The AMT and AAZ radiations represent separate radiations with no difference in speciation rates. Most taxa occur on rocks, with small geographic ranges relative to widespread generalist taxa across the vast central AAZ. Rock‐dwelling and generalist taxa differ morphologically, but only the lineage‐poor central AAZ taxa have accelerated evolution. This accords with increasing evidence that lineage and morphological diversity are poorly correlated, and suggests environmental heterogeneity and refugial dynamics have been more important than ecological release in elevating lineage diversity.     

Densely sampled phylogenetic analyses of the Lesser Short-toed Lark (Alaudala rufescens) — Sand Lark (A. raytal) species complex (Aves,Passeriformes) reveal cryptic diversity

The taxonomy of the Lesser/Asian Short-toed Lark Alaudala rufescens–cheleensis complex has been debated for decades, mainly because of minor morphological differentiation among the taxa within the complex, and different interpretations of the geographical pattern of morphological characters among different authors. In addition, there have been few studies based on non-morphological traits. It has recently been suggested based on a molecular study of the lark family Alaudidae that the Sand Lark A. raytal is nested within this complex. We here analysed mitochondrial cytochrome b (cyt b) from 130 individuals across the range of this complex (hereafter called Alaudala rufescens–raytal complex), representing all except two of the 18 currently recognized subspecies. We also analysed 11 nuclear markers from a subsample of these individuals, representing all of the clades found in the cyt b tree. Five primary clades were recovered, which confirmed that A. raytal is nested within this complex. Divergence time estimates among these five clades ranged from 1.76 to 3.16 million years (my; 95% highest posterior density [HPD] 1.0–4.51 my) or 1.99–2.53 my (95% HPD 0.96–4.3 my) in different analyses. Only four of the currently recognized subspecies were recovered as monophyletic in the cyt b tree. Our results call for a taxonomic revision, and we tentatively suggest that at least four species should be recognized, although we stress the need for an approach integrating molecular, morphological and other data that are not yet available.     

Hemiboea guangdongensis comb. & stat. nov., a cryptic species segregated from H. subcapitata (Gesneriaceae) based on morphological and molecular data

The taxonomic problem of cryptic species has long been recognized. Hemiboea subcapitata C. B. Clarke is a widespread and morphologically diverse species including two varieties, H. subcapitata var. subcapitata C. B. Clarke and H. subcapitata var. guangdongensis (Z. Y. Li) Z. Y. Li. However, genetic distance and molecular phylogenetic analyses based on nuclear ITS and four plastid DNA sequences (atpB‐rbcL, matK, rbcL, rpS16 intron) revealed that H. subcapitata var. guangdongensis is sister to H. subacaulis, and separated from H. subcapitata var. subcapitata, suggesting that it should be raised to the rank of an independent species as H. guangdongensis (Z. Y. Li) X. Q. Li & X. G. Xiang, comb. & stat. nov. Morphologically, the new species can be distinguished from H. subacaulis by its calyx 5‐sect from base, segments narrowly oblong‐lanceolate (versus calyx 5‐sect from base or 2‐lipped and adaxial lip 2‐lobed from below middle, segments ovate), peduncle glabrous (versus pubescent), and vermiform sclereids dispersed in leaf mesophyll (versus without sclereids).     

How many species of Hipposideros have occurred on Madagascar since the Late Pleistocene?

Populations of the Malagasy Hipposideros commersoni (family Hipposideridae) are threatened by deforestation and hunting. Maximum likelihood and Bayesian analysis of 148 cytochrome b sequences found this species to be paraphyletic and composed of three well‐supported monophyletic clades. Clades B and C form a monophyletic lineage that can be referred to H. commersoni; these two clades are separated by 6% sequence variation. Clade A represents a distinct evolutionary lineage separate (9–11% average sequence divergence) from H. commersoni (clades B and C) and is named herein as a new species, H ipposideros cryptovalorona sp. nov. In the phylogeny presented herein, this species is strongly associated with the outgroup taxa Hipposideros gigas and Hipposideros vittatus, both restricted to Africa. External, cranial and dental measurements taken from the same individuals used in the molecular study indicate no clear distinction in morphology amongst these three clades; this includes noseleaf structure and craniodental characteristics. Principal component analyses showed limited separation of the three clades. Comparison to a Quaternary fossil species from north‐west Madagascar, Hipposideros besaoka, found little morphological overlap between any of the three clades and this extinct species. Hence, at least three species of Hipposideros have occurred on Madagascar since the Late Pleistocene, two extant (H. commersoni s.s. and H. cryptovalorona sp. nov.) and one extinct (H. besaoka). © 2015 The Linnean Society of London