Molecular phylogenetics, vocalizations, and species limits in Celeus woodpeckers (Aves: Picidae)

Species limits and the evolutionary mechanisms that have shaped diversification of woodpeckers and allies (Picidae) remain obscure, as inter and intraspecific phylogenetic relationships have yet to be comprehensively resolved for most genera. Herein, we analyzed 5020 base pairs of nucleotide sequence data from the mitochondrial and nuclear genomes to reconstruct the evolutionary history of Celeus woodpeckers. Broad geographic sampling was employed to assess species limits in phenotypically variable lineages and provide a first look at the evolution of song and plumage traits in this poorly known Neotropical genus. Our results strongly support the monophyly of Celeus and reveal several novel relationships across a shallow phylogenetic topology. We confirm the close sister relationship between Celeus spectabilis and the enigmatic Celeus obrieni, both of which form a clade with Celeus flavus. The Mesoamerican Celeus castaneus was placed as sister to a Celeus undatus-grammicus lineage, with the species status of the latter drawn into question given the lack of substantial genetic, morphological, and vocal variation in these taxa. We recovered paraphyly in Celeus elegans; however, this result appears to be the consequence of mitochondrial introgression from Celeus lugubris considering the monophyly of elegans at the ?-FIBI7 locus. A second instance of paraphyly was observed in Celeus flavescens with deep genetic splits and substantial phenotypic variation indicating the presence of two distinct species in this broadly distributed lineage. As such, we advocate elevation of Celeus flavescens ochraceus to species status. Our analysis of Celeus vocalizations and plumage characters demonstrates a pattern of lability consistent with a relatively recent origin of the genus and potentially rapid speciation history.     

Nuclear locus divergence at the early stages of speciation in the Orchard Oriole complex

As two lineages diverge from one another, mitochondrial DNA should evolve fixed differences more rapidly than nuclear DNA due to its smaller effective population size and faster mutation rate. As a consequence, molecular systematists have focused on the criteria of reciprocal monophyly in mitochondrial DNA for delimiting species boundaries. However, mitochondrial gene trees do not necessarily reflect the evolutionary history of the taxa in question, and even mitochondrial loci are not expected to be reciprocally monophyletic when the speciation event happened very recently. The goal of this study was to examine mitochondrial paraphyly within the Orchard Oriole complex, which is composed of Icterus spurius (Orchard Oriole) and Icterus fuertesi (Fuertes' Oriole). We increased the geographic sampling, added four nuclear loci, and used a range of population genetic and coalescent methods to examine the divergence between the taxa. With increased taxon sampling, we found evidence of clear structure between the taxa for mitochondrial DNA. However, nuclear loci showed little evidence of population structure, indicating a very recent divergence between I. spurius and I. fuertesi. Another goal was to examine the genetic variation within each taxon to look for evidence of a past founder event within the I. fuertesi lineage. Based on the high amounts of genetic variation for all nuclear loci, we found no evidence of such an event – thus, we found no support for the possible founding of I. fuertesi through a change in migratory behavior, followed by peripheral isolates speciation. Our results demonstrate that these two taxa are in the earliest stages of speciation, at a point when they have fixed differences in plumage color that are not reflected in monophyly of the mitochondrial or nuclear DNA markers in this study. This very recent divergence makes them ideal for continued studies of species boundaries and the earliest stages of speciation.     

Phenotypic and genetic introgression across a moving woodpecker hybrid zone

In hybrid zones in which two divergent taxa come into secondary contact and interbreed, selection can maintain phenotypic diversity despite widespread genetic introgression. Red‐breasted (Sphyrapicus ruber) and red‐naped (S. nuchalis) sapsuckers meet and hybridize along a narrow contact zone that stretches from northern California to southern British Columbia. We found strong evidence for changes in the structure of this hybrid zone across time, with significant temporal shifts in allele frequencies and in the proportions of parental phenotypes across the landscape. In addition to these shifts, we found that differences in plumage predict genetic differences (R² = 0.80), suggesting that plumage is a useful proxy for assessing ancestry. We also found a significant bimodal distribution of hybrids across the contact zone, suggesting that premating barriers may be driving reproductive isolation, perhaps as a result of assortative mating based on plumage differences. However, despite evidence of selection and strong patterns of population structure between parental samples, we found only weak patterns of genetic divergence. Using museum specimens and genomic data, this study of sapsuckers provides insight into the ways in which phenotypic and genetic structure have changed over a 40‐year period, as well as insight into the mechanisms that may contribute to the maintenance of the hybrid zone over time.     

Molecular data and distribution dynamics indicate a recent and incomplete separation of manakins species of the genus Antilophia (Aves: Pipridae) in response to Holocene climate change

To determine a hypothetical scenario that accounts for the diversification of the two species of the genus Antilophia, we conducted multilocus molecular comparisons and species distribution modeling for the two taxa, which have distinct male plumage coloration patterns and allopatric geographic distributions, despite the high degree of genetic similarity indicated by recent studies. Three mitochondrial and three nuclear fragments were analyzed. The results indicate clear differences in the genetic diversity of the two species, but with ample sharing of haplotypes in all the markers analyzed, reflecting the absence of reciprocal monophyly, presumably due to the relatively recent and still incomplete separation of the two species. The paleoclimatic distribution models, together with the observed genetic profile indicate a recent process of divergence by geographic isolation in the ancestral populations of the two species. This scenario coincides with the recent climatic events of the South American dry diagonal, which involves the gallery forests of the Cerrado biome and the cloud forest enclaves of the seasonal tropical dry forest of the Caatinga between the late Pleistocene and the mid Holocene.     

Hidden endemism,deep polyphyly,and repeated dispersal across the Isthmus of Tehuantepec: Diversification of the White‐collared Seedeater complex (Thraupidae: Sporophila torqueola)

Phenotypic and genetic variation are present in all species, but lineages differ in how variation is partitioned among populations. Examining phenotypic clustering and genetic structure within a phylogeographic framework can clarify which biological processes have contributed to extant biodiversity in a given lineage. Here, we investigate genetic and phenotypic variation among populations and subspecies within a Neotropical songbird complex, the White‐collared Seedeater (Sporophila torqueola) of Central America and Mexico. We combine measurements of morphology and plumage patterning with thousands of nuclear loci derived from ultraconserved elements (UCEs) and mitochondrial DNA to evaluate population differentiation. We find deep levels of molecular divergence between two S. torqueola lineages that are phenotypically diagnosable: One corresponds to S. t. torqueola along the Pacific coast of Mexico, and the other includes S. t. morelleti and S. t. sharpei from the Gulf Coast of Mexico and Central America. Surprisingly, these two lineages are strongly differentiated in both nuclear and mitochondrial markers, and each is more closely related to other Sporophila species than to one another. We infer low levels of gene flow between these two groups based on demographic models, suggesting multiple independent evolutionary lineages within S. torqueola have been obscured by coarse‐scale similarity in plumage patterning. These findings improve our understanding of the biogeographic history of this lineage, which includes multiple dispersal events out of South America and across the Isthmus of Tehuantepec into Mesoamerica. Finally, the phenotypic and genetic distinctiveness of the range‐restricted S. t. torqueola highlights the Pacific Coast of Mexico as an important region of endemism and conservation priority.     

When taxonomy meets genomics: lessons from a common songbird

Taxonomy is being increasingly informed by genomics. Traditionally, taxonomy has relied extensively on phenotypic traits for the identification and delimitation of species, though with a growing influence from molecular phylogenetics in recent decades. Now, genomics opens up new and more powerful tools for analysing the evolutionary history and relatedness among species, as well as understanding the genetic basis for phenotypic traits and their role in reproductive isolation. New insights gained from genomics will therefore have major effects on taxonomic classifications and species delimitation. How a genomics approach can inform a flawed taxonomy is nicely exemplified by Mason & Taylor ( 2015 ) in this issue of Molecular Ecology. They studied redpolls, which comprise a genus (Acanthis) of fringillid finches with a wide distribution in the Holarctic region, and whose species taxonomy has been a matter of much controversy for decades (Fig.  1 ). Current authoritative checklists classify them into one, two or three species, and five or six subspecies, based largely on geographical differences in phenotypic traits. Previous studies, including a recent one of the subspecies on Iceland (Amouret et al. 2015 ), have found no evidence of differentiation between these taxa in conventional molecular markers. The lack of genetic structure has been interpreted as incomplete lineage sorting among rapidly evolving lineages. Now Mason & Taylor ( 2015 ), using a large data set of genomewide SNPs, verify that they all belong to a single gene pool with a common evolutionary history, and with little or no geographical structuring. They also show that phenotypic traits used in taxonomic classifications (plumage and bill morphology) are closely associated with polygenic patterns of gene expression, presumably driven by ecological selection on a few regulatory genes. Several lessons can be learned from this study. Perhaps the most important one for taxonomy is the risk of taxonomic inflation resulting from overemphasizing phenotypic traits under local adaptation and ignoring a lack of phylogenetic signal in molecular markers.     

Parallel plumage colour evolution and introgressive hybridization in wheatears

Genetic and phenotypic mosaics, in which various phenotypes and different genomic regions show discordant patterns of species or population divergence, offer unique opportunities to study the role of ancestral and introgressed genetic variation in phenotypic evolution. Here, we investigated the evolution of discordant phenotypic and genetic divergence in a monophyletic clade of four songbird taxa—pied wheatear (O. pleschanka), Cyprus wheatear (Oenanthe cypriaca), and western and eastern subspecies of black‐eared wheatear (O. h. hispanica and O. h. melanoleuca). Phenotypically, black back and neck sides distinguish pied and Cyprus wheatears from the white‐backed/necked black‐eared wheatears. Meanwhile, mitochondrial variation only distinguishes western black‐eared wheatear. In the absence of nuclear genetic data, and given frequent hybridization among eastern black‐eared and pied wheatear, it remains unclear whether introgression is responsible for discordance between mitochondrial divergence patterns and phenotypic similarities, or whether plumage coloration evolved in parallel. Multispecies coalescent analyses of about 20,000 SNPs obtained from RAD data mapped to a draft genome assembly resolve the species tree, provide evidence for the parallel evolution of colour phenotypes and establish western and eastern black‐eared wheatears as independent taxa that should be recognized as full species. The presence of the entire admixture spectrum in the Iranian hybrid zone and the detection of footprints of introgression from pied into eastern black‐eared wheatear beyond the hybrid zone despite strong geographic structure of ancestry proportions furthermore suggest a potential role for introgression in parallel plumage colour evolution. Our results support the importance of standing heterospecific and/or ancestral variation in phenotypic evolution.     

Species designation of the Bruneau Dune tiger beetle (Cicindela waynei) is supported by phylogenetic analysis of mitochondrial DNA sequence data

Beetles comprise nearly one quarter of described species and show high levels of morphological and ecological diversification. Because of their wide distribution, ease of detection, and correlation of species richness patterns with other taxa, tiger beetles have been recommended for use as a global indicator of regional biodiversity, requiring accurate taxonomic designations. The Bruneau Dune tiger beetle (Cicindela waynei), whose habitat consists of an isolated dune field in southern Idaho, was recently described as a distinct species from the St. Anthony Dunes tiger beetle (C. arenicola) based on morphological characteristics. While these characteristics include distinct differences in genital morphology that could indicate intrinsic reproductive isolation, morphological characteristics have sometimes been misleading in tiger beetle taxonomy. To evaluate genetic support for this species designation, we analyzed 1,751 base pairs of mitochondrial DNA sequence from 147 tiger beetles collected throughout the range of both C. arenicola and C. waynei. Maximum-likelihood and Bayesian phylogenetic analyses indicated monophyly for C. waynei on a well-supported, short branch nested within C. arenicola. Bayesian species delimitation analyses strongly supported C. waynei as a distinct species (speciation probability = 1.0) with the estimated time of divergence ca. 14,500–67,000 years ago. This lack of reciprocal monophyly and recency of speciation is consistent with C. waynei as a member of an evolutionary front where speciation has occurred at a rapid rate. Mitochondrial sequence data supports the species designation of C. waynei, emphasizing the need to determine appropriate management for this species and its restricted habitat.     

Morphological and genetic differentiation of Eremina desertorum (Gastropoda,Pulmonata, Helicidae) in Egypt

To understand the processes that result in morphological and genetic diversity, we studied the differentiation of the land snails Eremina d. desertorum and Eremina desertorum irregularis in the deserts of northern Egypt. These two taxa are differentiated with regard to shell size and shape and are separated by a narrow hybrid zone west of Alexandria. The lack of differences in the genitalia and the lack of reciprocal monophyly of the mitochondrial haplotypes of E. d. desertorum and E. desertorum irregularis support their classification as subspecies rather than distinct species. Low genetic distances indicate that the differentiation is probably less than half a million years old. The genetic data indicate a population expansion in agreement with other evidence that the Nile region in northern Egypt was more humid well into historical times than today. Shell size and shape are correlated with a climatic gradient from cooler and more humid conditions along the Mediterranean coast to arid and hot conditions in the interior. The decrease of body size with decreasing precipitation and increasing temperature might be explained by limited time for food intake in the more arid regions. The shape differences between the taxa are partly an indirect consequence of selection for body size, but are also directly affected by selection for reduction of aperture size.     

Assessment of species limits in African ‘brown buntings’ (Emberiza,Passeriformes) based on mitochondrial and nuclear sequence data

We estimated a phylogeny for 10 taxa currently placed in four polytypic species that collectively encompass the African ‘brown buntings’: Cape Bunting Emberiza capensis, Cinnamon‐breasted Bunting Emberiza tahapisi, Lark‐like Bunting Emberiza impetuani and House Bunting Emberiza striolata. We made use of the mitochondrial cytochrome b gene and the nuclear introns 6–7 of ornithine decarboxylase (ODC), and intron 2 of myoglobin. There was substantial cytochrome b sequence divergence between taxa currently treated as conspecific: sahari vs. striolata (2.6–3.1% (uncorrected‐p); 3.0–3.6% (HKY + I)), and goslingi vs. tahapisi (4.4–4.7% (uncorrected‐p); 5.4–5.9% (HKY + I)). The degree of divergence of the nuclear loci among taxa was limited, and these loci lacked reciprocal monophyly, most likely as a consequence of incomplete lineage sorting. A single representative of the taxon septemstriata, generally treated as a member of the dark‐throated tahapisi group, here appears to be genetically consistent with the grey‐throated goslingi, and may be of hybrid origin. All other taxa allocated to E. striolata and E. tahapisi make up four reciprocally monophyletic groups consistent with sahari, striolata, tahapisi and goslingi, respectively. The extent of genetic evidence suggests that these taxa have been evolving as separate evolutionary lineages for a long time. This is further manifested in several morphological and vocal characteristics described previously, and we propose that these divergent taxa be treated as separate species: Cinnamon‐breasted Bunting Emberiza tahapisi, Gosling's Bunting Emberiza goslingi, Striolated Bunting Emberiza striolata and House Bunting Emberiza sahari. We do not propose any taxonomic changes regarding Emberiza impetuani or Emberiza capensis.     

火龙果种质资源果实特性的遗传多样性分析

为筛选火龙果(Hylocereus undatus)优良种质资源,对22份种质资源果实的表型性状、农艺性状、品质性状进行遗传多样性分析。结果表明,火龙果种质资源果实的表型性状、农艺性状和品质性状具有丰富的遗传多样性和较高的变异性,表型性状的多样性指数(H′)为0～1.04,品质性状为0.40～2.01;农艺性状的变异系数(CV)为0.06～0.38,品质性状为0.01～0.62。聚类分析表明,在遗传距离为15时,火龙果22份种质资源可分为5类,说明不同资源间亲缘关系较远。这为发掘火龙果的育种潜力,筛选优异基因资源,改良种质奠定了基础。     

Discordance between morphological and molecular species boundaries among Caribbean species of the reef sponge Callyspongia

Sponges are among the most species‐rich and ecologically important taxa on coral reefs, yet documenting their diversity is difficult due to the simplicity and plasticity of their morphological characters. Genetic attempts to identify species are hampered by the slow rate of mitochondrial sequence evolution characteristic of sponges and some other basal metazoans. Here we determine species boundaries of the Caribbean coral reef sponge genus Callyspongia using a multilocus, model‐based approach. Based on sequence data from one mitochondrial (COI), one ribosomal (28S), and two single‐copy nuclear protein‐coding genes, we found evolutionarily distinct lineages were not concordant with current species designations in Callyspongia. While C. fallax, C. tenerrima, and C. plicifera were reciprocally monophyletic, four taxa with different morphologies (C. armigera, C. longissima, C. eschrichtii, and C. vaginalis) formed a monophyletic group and genetic distances among these taxa overlapped distances within them. A model‐based method of species delimitation supported collapsing these four into a single evolutionary lineage. Variation in spicule size among these four taxa was partitioned geographically, not by current species designations, indicating that in Callyspongia, these key taxonomic characters are poor indicators of genetic differentiation. Taken together, our results suggest a complex relationship between morphology and species boundaries in sponges.     

Evolutionary trade‐off between naturally‐ and sexually‐selected melanin‐based colour traits in worldwide barn owls and allies

Natural selection typically constrains the evolution of sexually‐selected characters. The evolution of naturally‐ and sexually‐selected traits can be intertwined if they share part of their genetic machinery or if sex traits impair foraging success or increase the risk of depredation. The present study investigated phenotypic correlations between naturally‐ and sexually‐selected plumage traits in the Tytonidae (barn owls, grass owls, and masked owls). Phenotypic correlations indicate the extent to which selection on one trait will indirectly influence the evolution of another trait. In this group of birds, the ventral body side varies from white to dark reddish, a naturally‐selected pheomelanin‐based colour trait with important roles in predator–prey interactions. Owls also exhibit eumelanin‐based black spots, for which number and size signal different aspects of individual quality and are used in mate choice. These three plumage traits are strongly heritable and sexually dimorphic, with females being on average darker reddish and more spotted than males. Phenotypic correlations were measured between these three plumage traits in 3958 free‐living barn owls in Switzerland and 10 670 skin specimens from 34 Tyto taxa preserved in museums. Across Tyto taxa, the sexually‐selected plumage spottiness was positively correlated with the naturally‐selected reddish coloration, with redder birds being more heavily spotted. This suggests that they are genetically constrained or that natural and sexual selection are not antagonistically exerted on plumage traits. In a large sample of Swiss nestlings and within 34 Tyto taxa, the three plumage traits were positively correlated. The production of melanin pigments for one plumage trait is therefore not traded off against the production of melanin pigments for another plumage trait. Only in the most heavily‐spotted Tyto taxa do larger‐spotted individuals display fewer spots. This indicates that, at some threshold value, the evolution of many spots constrains the evolution of large spots. These analyses raise the possibility that different combinations of melanin‐based plumage traits may not be selectively equivalent.     

Taxonomy of the Narcissus Flycatcher Ficedula narcissina complex: an integrative approach using morphological,bioacoustic and multilocus DNA data

The taxonomy of the Narcissus Flycatcher Ficedula narcissina–Yellow‐rumped Flycatcher Ficedula zanthopygia complex from East Asia has long been debated. Most authors recognize two species: F. narcissina, with the subspecies narcissina (most of Japan and Sakhalin Island), owstoni (south Japanese islands) and elisae (northeast China) and F. zanthopygia (monotypic), although species status has been proposed for elisae and sometimes for owstoni. Here, we revise the taxonomy of this complex based on an integrative approach utilizing morphology, songs and mitochondrial and nuclear DNA for all taxa. All taxa were diagnosably different in plumage, and there were also structural differences among them, although the northernmost populations of owstoni (sometimes recognized as jakuschima and shonis) were somewhat intermediate in plumage, structure and male plumage maturation between southern populations of owstoni and narcissina. All taxa had different songs, and a discriminant function analysis of four song variables correctly classified 100% of all songs. A strongly supported phylogeny was recovered based on three mitochondrial genes and three nuclear introns (total of 3543 bp), revealing a sister relationship between F. zanthopygia and the other taxa, between F. n. narcissina and F. n. owstoni, and between F. n. elisae and F. n. narcissina + F. n. owstoni. The corrected COI distances among the three F. narcissina subspecies ranged from 2.8% (narcissina–owstoni) to 8.2% (narcissina–elisae). We suggest that the congruent differences in multiple independent traits and the deep genetic divergences among the four taxa in the F. narcissina–F. zanthopygia complex support treatment of all of these taxa as separate species. However, we acknowledge the paucity of data for F. owstoni and recommend further studies of this taxon. We suggest listing both F. elisae and F. owstoni, which have small and fragmented populations, as globally threatened.     

Morphotypes or distinct species? A multilocus assessment of two East Asian scimitar babblers (Aves,Timaliidae)

In birds, widespread species complexes often exhibit dramatic plumage differences across their distribution, which can give rise to discordance between morphotypes and phylogroups. Accurate identification of species diversity may require an integrated approach in which multilocus genetic data are used for inference and further corroborated by ecological, morphometric or behavioural data. Pomatorhinus gravivox and P. swinhoei, which were formerly considered component races of P. erythrogenys, were recently split using a delimitation system that mainly relied on the quantification of differences in phenotypic traits. We therefore carried out a reassessment of this taxonomic recommendation by conducting phylogenetic and population genetic analyses with multilocus genetic data. A deep mitochondrial split with a Kimura 2-parameter distance of 0.061 was observed, mainly corresponding to the two morphologically defined species. However, one individual from P. swinhoei harboured a haplotype of P. gravivox. Individual-based analyses of nuclear loci identified two distinct clusters that were exactly congruent with the two species. BPP delimitation also provided support for the separation. These congruencies support the notion that these two taxa are best regarded as two separate species. The presence of the P. gravivox mitochondrial haplotype in P. swinhoei was most likely a result of hybridization, due to the clear separation of nuclear loci. The speciation might be attributed to paleoclimatic changes but requires further evaluation due to the likelihood of ecological speciation. This study was in accordance with the results inferred from the quantitative system but highlighted the importance of sampling various data, especially in contact zones, in the study of taxonomy and speciation history.     

Mitochondrial capture and incomplete lineage sorting in the diversification of balitorine loaches (Cypriniformes,Balitoridae) revealed by mitochondrial and nuclear genes

Tang, Q.‐Y., Liu, S.‐Q., Yu, D., Liu, H.‐Z. & Danley, P.D. (2012) Mitochondrial capture and incomplete lineage sorting in the diversification of balitorine loaches (Cypriniformes, Balitoridae) revealed by mitochondrial and nuclear genes. —Zoologica Scripta, 41, 233–247. Understanding the diversification of species is a central goal of evolutionary biological studies. One powerful tool to investigate the speciation process is molecular systematics. Here, we use molecular methods to investigate the evolution of balitorine loaches belonging to two genera, Lepturichthys and Jinshaia. Both genera contain only two species (Lepturichthys fimbriata, Lepturichthys dolichopterus and Jinshaia sinensis and Jinshaia abbreviata), all of which are endemic to China. These species share many morphological and ecological characters and exhibit overlapping distributions in the Upper Yangtze River. In this study, we used two mitochondrial genes (Cytb and COI) and one nuclear gene (RAG1) to investigate the phylogenetic relationships within and between these two genera. Phylogenetic analyses and network construction based on mitochondrial and nuclear genes consistently supported the monophyly of Jinshaia. In contrast, the mitochondrial and nuclear genes yielded conflicting results in Lepturichthys. The phylogenetic analyses of mitochondrial sequences identify two distinct Lepturichthys lineages, Lepturichthys A and Lepturichthys B. Lepturichthys A includes most of L. fimbriata individuals from the Upper Yangtze River and is the sister group to all Jinshaia species. Lepturichthys B consists of the remaining L. fimbriata individuals from the Upper and Middle Yangtze River, and all L. dolichopterus individuals from the Minjiang River in Southeastern China. However, the analysis of the nuclear sequence indicates that the genus Lepturichthys is monophyletic and is only distantly related to Jinshaia. This incongruence suggests that introgressive hybridization might have occurred between L. fimbriata (Lepturichthys A) and Jinshaia species. As a result of this hybridization event, L. fimbriata captured the mitochondrial genome of the sympatric Jinshaia species. This capture event appears to have occurred at least 1.74 million years ago. Additionally, L. fimbriata appears to be paraphyletic; the nuclear data indicated that L. dolichopterus forms a monophyletic clade nested within L. fimbriata. Because L. dolichopterus and L. fimbriata are allopatric and hybridization may not be possible, we suggest that the observed paraphyly of L. fimbriata is a product of incomplete lineage sorting. In addition, the reciprocal monophyly of J. sinensis and J. abbreviata could not be resolved. This may be the result of interspecific hybridization as these species occur sympatrically. However, incomplete lineage sorting may have caused the observed topology of the Jinshaia species. The data presented here illustrate the complex evolutionary history of the balitorine loach species: intergeneric hybridization and interspecific hybridization have likely occurred in this lineage. In addition, possible incomplete lineage sorting may further obscure the evolutionary history of this group. The complex relationships of the balitorine loaches provide a rich evolutionary system to study the creation of sympatric and sister species.