Monophyletic Radiation Research Articles

Evolution of Placentation in Eugongylini (Squamata: Scincidae): Ontogeny of Extraembryonic Membranes in Oviparous and Viviparous Species of New Zealand.

New Zealand scincid lizards, genus Oligosoma, represent a monophyletic radiation of a clade, Eugongylini, of species distributed geographically throughout the South Pacific with major radiations in Australia and New Caledonia. Viviparity has evolved independently on multiple occasions within these lineages. Studies of Australian species have revealed that placental specializations resulting in substantial placentotrophy have evolved in two lineages. The pattern of extraembryonic membrane development of oviparous species differs from viviparous species and identical placental architecture has evolved in both placentotrophic lineages. We analyzed extraembryonic membrane development in two New Zealand species, the sole oviparous species, Oligosoma suteri, and placental development of a representative viviparous species, Oligosoma polychroma, using histological techniques. We conclude that these two species share a basic pattern of extraembryonic membrane development with other squamates. Comparisons with Australian species indicate that morphogenesis of the yolk sac of O. suteri results in an elaborate structure previously known only in Oligosoma lichenigerum with a geographic distribution on Lord Howe Island and Norfolk Island. This finding supports a close relationship between these two taxa. We conclude also that the pattern of placental development of O. polychroma is identical to that of viviparous species of Australia. The terminal placental stage for each of these lineages includes a chorioallantoic placenta and an elaborate omphaloplacenta. This level of homoplasy in placental evolution is consistent with a hypothesis that selection favors regional differentiation of the maternal-embryonic interface and that the omphaloplacenta is an adaptation for histotrophic transport.

Nucleotide sequences of mitochondrial cytochrome b gene for phylogeny of some species of Rodentia

Order Rodentia contains approximately half of all living mammalian species. Most of the living species diversity within rodents is within five monophyletic radiations: Hystricognathi, Sciuridae, Geomyoidea, Dipodidae, and Muroidea. The samples collected across different areas of Egypt were analyzed by means of mitochondrial cytochrome b gene sequence analysis to ascertain the true taxonomic status between the studied species. For phylogenetic analysis, the cytochrome b sequences from this study were combined with previously published data. This study reveals that all species were divided into two main clades, the first for the Gerbillinae taxon and the second for the other studied genera in the molecular phylogenetic trees and demonstrates that Gerbillus species form a sister group with Dipodillus species. The phylogenetic relationships specified for the murine genera. Clustering was obtained between Mus and Rattus as well as in all Gerbillinae species. This study provides the first insight into the genetic diversity of some rodents in Egypt.

Transcriptome of Epibiont Saccharibacteria Nanosynbacter lyticus Strain TM7x During the Establishment of Symbiosis.

Saccharibacteria Nanosynbacter lyticus strain TM7x is a member of the broadly distributed candidate phylum radiation. These bacteria have ultrasmall cell sizes, have reduced genomes, and live as epibionts on the surfaces of other bacteria. The mechanisms by which they establish and maintain this relationship are not yet fully understood. The transcriptomes of the epibiont TM7x and its host bacteria Schaalia odontolytica strain XH001 were captured across the establishment of symbiosis during both the initial interaction and stable symbiosis. The results showed a dynamic interaction with large shifts in gene expression for both species between the initial encounter and stable symbiosis, notably in transporter genes. During stable symbiosis, the host XH001 showed higher gene expression for peptidoglycan biosynthesis, mannosylation, cell cycle and stress-related genes, whereas it showed lower expression of chromosomal partitioning genes. This was consistent with the elongated cell shape seen in XH001 infected with TM7x and our discovery that infection resulted in thickened cell walls. Within TM7x, increased pili, type IV effector genes, and arginine catabolism/biosynthesis gene expression during stable symbiosis implied a key role for these functions in the interaction. Consistent with its survival and persistence in the human microbiome as an obligate epibiont with reduced de novo biosynthetic capacities, TM7x also showed higher levels of energy production and peptidoglycan biosynthesis, but lower expression of stress-related genes, during stable symbiosis. These results imply that TM7x and its host bacteria keep a delicate balance in order to sustain an episymbiotic lifestyle. IMPORTANCE Nanosynbacter lyticus type strain TM7x is the first cultivated member of the Saccharibacteria and the candidate phyla radiation (CPR). It was discovered to be ultrasmall in cell size with a highly reduced genome that establishes an obligate epibiotic relationship with its host bacterium. The CPR is a large, monophyletic radiation of bacteria with reduced genomes that includes Saccharibacteria. The vast majority of the CPR have yet to be cultivated, and our insights into these unique organisms to date have been derived from only a few Saccharibacteria species. Being obligate parasites, it is unknown how these ultrasmall Saccharibacteria, which are missing many de novo biosynthetic pathways, are maintained at a high prevalence within the human microbiome as well as in the environment.

A molecular framework for the systematics of the Mediterranean spindle-shells (Gastropoda, Neogastropoda, Fasciolariidae, Fusininae)

A remarkably high diversity of native small spindle-shells (Gastropoda, Fasciolariidae, Fusininae) has been recently inventoried in the Mediterranean Sea, with 23 species identified based on shell morphology. They have almost invariably been classified in the genus Fusinus, and a few of them recently moved to other genera (Aptyxis Troschel 1868, Aegeofusinus Russo, 2017 and Gracilipurpura Jousseaume, 1880), mostly based on the sole shell features. We have reconstructed a molecular phylogenetic framework for the Mediterranean Fusininae, focusing on native species representative of the genus-level taxa. Our results confirmed that Fusinus s.s. (type species Murex colus Linnaeus, 1758) should be restricted to a group of large-shelled species from the Indo-West Pacific and does not fit any of the small-shelled Mediterranean fusinines. We confirm that Murex syracusanus Linnaeus, 1758 represents a distinct lineage, and show that for all the remaining species the pattern is suggestive of a single monophyletic radiation of small Mediterranean fusinines, for which the name Pseudofusus Monterosato, 1884 must be used.

A new sectional classification of Lachenalia (Asparagaceae) based on a multilocus DNA phylogeny

AbstractLachenalia (Asparagaceae; Scilloideae; Hyacintheae) is a large and morphologically diverse genus of more than 140 bulbous species endemic to southern Africa. Previous attempts to infer a well‐resolved and robustly supported phylogeny of Lachenalia using Sanger sequencing of candidate loci and/or morphological characters have been largely unsuccessful. Consequently, the current infrageneric classification is artificial, and there is a need to explore alternative avenues to produce a phylogenetic classification. In this paper, we present a novel phylogenetic hypothesis for Lachenalia inferred using maximum likelihood and coalescent‐based species tree estimation (ASTRAL) as applied to 378 hybrid‐enrichment loci. Our tree is well resolved and well supported, providing strong support for a monophyletic radiation of the genus in southern Africa and a solid foundation for a revised infrageneric classification. The well‐supported placement of L. isopetala Jacq. as sister to Lachenalia + Massonia supports the establishment of a new monotypic genus, Pseudolachenalia, to accommodate this species. Conversely, the inclusion of species previously classified as Polyxena within the Lachenalia clade supports the transfer of these species to Lachenalia. Within Lachenalia, the delimitation of subgenera and sections is complicated by the highly imbalanced character of the phylogeny and by the high levels of homoplasy shown by most morphological characters traditionally used to delimit species in this group. Nonetheless, we propose an infrageneric taxonomy comprising 10 morphologically distinct, monophyletic sections. The largest of these, L. sect. Lachenalia, is further divided into 13 more‐or‐less diagnosable, monophyletic subsections. Keys to the sections of Lachenalia, and to the subsections of L. sect. Lachenalia, are provided.

Between a Rock and a Hard Polytomy: Phylogenomics of the Rock-Dwelling Mbuna Cichlids of Lake Malaŵi.

Whole genome sequences are beginning to revolutionize our understanding of phylogenetic relationships. Yet, even whole genome sequences can fail to resolve the evolutionary history of the most rapidly radiating lineages, where incomplete lineage sorting, standing genetic variation, introgression, and other factors obscure the phylogenetic history of the group. To overcome such challenges, one emerging strategy is to integrate results across different methods. Most such approaches have been implemented on reduced representation genomic data sets, but whole genomes should provide the maximum possible evidence approach. Here, we test the ability of single nucleotide polymorphisms extracted from whole genome resequencing data, implemented in an integrative genomic approach, to resolve key nodes in the phylogeny of the mbuna, rock-dwelling cichlid fishes of Lake Malaŵi, which epitomize the phylogenetic intractability that often accompanies explosive lineage diversification. This monophyletic radiation has diversified at an unparalleled rate into several hundred species in less than 2 million years. Using an array of phylogenomic methods, we consistently recovered four major clades of mbuna, but a large basal polytomy among them. Although introgression between clades apparently contributed to the challenge of phylogenetic reconstruction, reduction of the data set to nonintrogressed sites still did not help to resolve the basal polytomy. On the other hand, relationships among six congeneric species pairs were resolved without ambiguity, even in one case where existing data led us to predict that resolution would be difficult. We conclude that the bursts of diversification at the earliest stages of the mbuna radiation may be phylogenetically unresolvable, but other regions of the tree are phylogenetically clearly supported. Integration of multiple phylogenomic approaches will continue to increase confidence in relationships inferred from these and other whole-genome data sets. [Incomplete lineage sorting; introgression; linkage disequilibrium; multispecies coalescence; rapid radiation; soft polytomy.]

Widespread introgression across a phylogeny of 155 Drosophila genomes

Genome-scale sequence data have invigorated the study of hybridization and introgression, particularly in animals. However, outside of a few notable cases, we lack systematic tests for introgression at a larger phylogenetic scale across entire clades. Here, we leverage 155 genome assemblies from 149 species to generate a fossil-calibrated phylogeny and conduct multilocus tests for introgression across 9 monophyletic radiations within the genus Drosophila. Using complementary phylogenomic approaches, we identify widespread introgression across the evolutionary history of Drosophila. Mapping gene-tree discordance onto the phylogeny revealed that both ancient and recent introgression has occurred across most of the 9 clades that we examined. Our results provide the first evidence of introgression occurring across the evolutionary history of Drosophila and highlight the need to continue to study the evolutionary consequences of hybridization and introgression in this genus and across the tree of life.

Analysis of Bobbing Displays in the Grahami Series Anoles from Jamaica and Grand Cayman

Behavioral biologists have long been fascinated with the diversity of animal signals produced in the contexts of courtship and same-sex competition. In these contexts many lizards engage in conspicuous bobbing displays, and numerous studies have been devoted to describing these displays. Traditionally, bobbing displays are partitioned into units whose durations (and sometimes head amplitudes) are measured. Recently, Macedonia et al. (2019) introduced use of the Discrete Fourier Transform (DFT) as an alternative to unit-based variables for characterizing species-specific traits in display structure of Galápagos Lava Lizards (Microlophus spp.). The relative success of the two methods was not compared directly, however, because the homology of display units among species was uncertain. Here we overcome this problem using the “grahami series” of Anolis lizards—a monophyletic radiation of seven species on Jamaica and Grand Cayman. Our study had three primary goals. Our first goal was to discover whether DFT-based measures, unit-based measures, or their combination provided the best means to capture taxon-specific distinctiveness in display structure. To this end, we quantified bobbing displays and used nested analyses of variance (ANOVAs) to determine if particular variables were reliably superior at differentiating populations within a species. We then used principal components analysis to reduce the number of measurement variables, and entered the components into discriminant function analyses to determine which approach best discriminated among taxa. Results showed that no one type of measurement, or measurement combination, emerged as being consistently better at discriminating taxa across comparisons. Our second goal was to test a hypothesis that arose from our findings in Galápagos Lava Lizards—that the DFT may decrease in effectiveness as bobbing display structure increases in complexity. For this test we used four simple and compound display types from the species Anolis reconditus. Results of discriminant function analyses provided mixed support for the hypothesis, and we suggest that a definitive test of DFT performance and display complexity should utilize synthetic displays in which attributes of display structure are varied systematically. Last, we show how bobbing display structure maps onto alternative DNA-based phylogenies of the grahami series anoles. Whereas some species produced derived display types unanticipated from displays of more basal species in this adaptive radiation, others exhibited features that linked them to a particular population of a species in their clade.

Using target sequence capture to improve the phylogenetic resolution of a rapid radiation in New Zealand Veronica.

Recent, rapid radiations present a challenge for phylogenetic reconstruction. Fast successive speciation events typically lead to low sequence divergence and poorly resolved relationships with standard phylogenetic markers. Target sequence capture of many independent nuclear loci has the potential to improve phylogenetic resolution for rapid radiations. Here we applied target sequence capture with 353 protein-coding genes (Angiosperms353 bait kit) to Veronica sect. Hebe (common name hebe) to determine its utility for improving the phylogenetic resolution of rapid radiations. Veronica section Hebe originated 5-10 million years ago in New Zealand, forming a monophyletic radiation of ca 130 extant species. We obtained approximately 150 kbp of 353 protein-coding exons and an additional 200 kbp of flanking noncoding sequences for each of 77 hebe and two outgroup species. When comparing coding, noncoding, and combined data sets, we found that the latter provided the best overall phylogenetic resolution. While some deep nodes in the radiation remained unresolved, our phylogeny provided broad and often improved support for subclades identified by both morphology and standard markers in previous studies. Gene-tree discordance was nonetheless widespread, indicating that additional methods are needed to disentangle fully the history of the radiation. Phylogenomic target capture data sets both increase phylogenetic signal and deliver new insights into the complex evolutionary history of rapid radiations as compared with traditional markers. Improving methods to resolve remaining discordance among loci from target sequence capture is now important to facilitate the further study of rapid radiations.

Analysis of multiple chromosomal rearrangements in the genome of Willisornis vidua using BAC-FISH and chromosome painting on a supposed conserved karyotype

BackgroundThamnophilidae birds are the result of a monophyletic radiation of insectivorous Passeriformes. They are a diverse group of 225 species and 45 genera and occur in lowlands and lower montane forests of Neotropics. Despite the large degree of diversity seen in this family, just four species of Thamnophilidae have been karyotyped with a diploid number ranging from 76 to 82 chromosomes. The karyotypic relationships within and between Thamnophilidae and another Passeriformes therefore remain poorly understood. Recent studies have identified the occurrence of intrachromosomal rearrangements in Passeriformes using in silico data and molecular cytogenetic tools. These results demonstrate that intrachromosomal rearrangements are more common in birds than previously thought and are likely to contribute to speciation events. With this in mind, we investigate the apparently conserved karyotype of Willisornis vidua, the Xingu Scale-backed Antbird, using a combination of molecular cytogenetic techniques including chromosome painting with probes derived from Gallus gallus (chicken) and Burhinus oedicnemus (stone curlew), combined with Bacterial Artificial Chromosome (BAC) probes derived from the same species. The goal was to investigate the occurrence of rearrangements in an apparently conserved karyotype in order to understand the evolutionary history and taxonomy of this species. In total, 78 BAC probes from the Gallus gallus and Taeniopygia guttata (the Zebra Finch) BAC libraries were tested, of which 40 were derived from Gallus gallus macrochromosomes 1–8, and 38 from microchromosomes 9–28.ResultsThe karyotype is similar to typical Passeriformes karyotypes, with a diploid number of 2n = 80. Our chromosome painting results show that most of the Gallus gallus chromosomes are conserved, except GGA-1, 2 and 4, with some rearrangements identified among macro- and microchromosomes. BAC mapping revealed many intrachromosomal rearrangements, mainly inversions, when comparing Willisornis vidua karyotype with Gallus gallus, and corroborates the fissions revealed by chromosome painting.ConclusionsWillisornis vidua presents multiple chromosomal rearrangements despite having a supposed conservative karyotype, demonstrating that our approach using a combination of FISH tools provides a higher resolution than previously obtained by chromosome painting alone. We also show that populations of Willisornis vidua appear conserved from a cytogenetic perspective, despite significant phylogeographic structure.

The roles of vicariance and isolation by distance in shaping biotic diversification across an ancient archipelago: evidence from a Seychelles caecilian amphibian

BackgroundIsland systems offer excellent opportunities for studying the evolutionary histories of species by virtue of their restricted size and easily identifiable barriers to gene flow. However, most studies investigating evolutionary patterns and processes shaping biotic diversification have focused on more recent (emergent) rather than ancient oceanic archipelagos. Here, we focus on the granitic islands of the Seychelles, which are unusual among island systems because they have been isolated for a long time and are home to a monophyletic radiation of caecilian amphibians that has been separated from its extant sister lineage for ca. 65–62 Ma. We selected the most widespread Seychelles caecilian species, Hypogeophis rostratus, to investigate intraspecific morphological and genetic (mitochondrial and nuclear) variation across the archipelago (782 samples from nine islands) to identify patterns and test processes that shaped their evolutionary history within the Seychelles.ResultsOverall a signal of strong geographic structuring with distinct northern- and southern-island clusters were identified across all datasets. We suggest that these distinct groups have been isolated for ca. 1.26 Ma years without subsequent migration between them. Populations from the somewhat geographically isolated island of Frégate showed contrasting relationships to other islands based on genetic and morphological data, clustering alternatively with northern-island (genetic) and southern-island (morphological) populations.ConclusionsAlthough variation in H. rostratus across the Seychelles is explained more by isolation-by-distance than by adaptation, the genetic-morphological incongruence for affinities of Frégate H. rostratus might be caused by local adaptation over-riding the signal from their vicariant history. Our findings highlight the need of integrative approaches to investigate fine-scale geographic structuring to uncover underlying diversity and to better understand evolutionary processes on ancient, continental islands.

Undinarchaeota illuminate DPANN phylogeny and the impact of gene transfer on archaeal evolution

The recently discovered DPANN archaea are a potentially deep-branching, monophyletic radiation of organisms with small cells and genomes. However, the monophyly and early emergence of the various DPANN clades and their role in life’s evolution are debated. Here, we reconstructed and analysed genomes of an uncharacterized archaeal phylum (Candidatus Undinarchaeota), revealing that its members have small genomes and, while potentially being able to conserve energy through fermentation, likely depend on partner organisms for the acquisition of certain metabolites. Our phylogenomic analyses robustly place Undinarchaeota as an independent lineage between two highly supported ‘DPANN’ clans. Further, our analyses suggest that DPANN have exchanged core genes with their hosts, adding to the difficulty of placing DPANN in the tree of life. This pattern can be sufficiently dominant to allow identifying known symbiont-host clades based on routes of gene transfer. Together, our work provides insights into the origins and evolution of DPANN and their hosts.

Systematics of a survivor: the Cambrian kingstoniid trilobite Blountia Walcott,1916 across the Marjuman-Steptoean (Guzhangian-Paibian) extinction intervalin Laurentian North America.

The Cambrian (Marjuman-Steptoean; Guzhangian-Paibian) kingstoniid trilobite Blountia Walcott, 1916 is distributed widely in shelf strata of Laurentian North America. Species known from Marjuman formations were lost at the mass extinction at the end of that stage. New species entered the succession during and after the extinction interval, only to disappear within the Aphelaspis Zone of the lower part of the Steptoean Stage. Steptoean species and several uppermost Marjuman (Crepicephalus Zone) species are treated in this monograph. New collections and revision of type and other archival material increase the number of species in Steptoean strata from two to six. Phylogenetic analysis supports monophyly of Blountia and Maryvillia Walcott, 1916; Blountina Lochman, in Lochman Duncan, 1944 is retained as a monotypic taxon. Steptoean species do not form a single subclade within the cladogram, so there is no evidence for a simple monophyletic radiation following the end-Marjuman extinction. New species are Blountia angelae, B. morgancreekensis, B. nevadensis, B. newfoundlandensis, and B. tennesseensis.

Genomic dissection of an extended phenotype: Oak galling by a cynipid gall wasp.

Galls are plant tissues whose development is induced by another organism for the inducer's benefit. 30,000 arthropod species induce galls, and in most cases the inducing effectors and target plant systems are unknown. Cynipid gall wasps are a speciose monophyletic radiation that induce structurally complex galls on oaks and other plants. We used a model system comprising the gall wasp Biorhiza pallida and the oak Quercus robur to characterise inducer and host plant gene expression at defined stages through the development of galled and ungalled plant tissues, and tested alternative hypotheses for the origin and type of galling effectors and plant metabolic pathways involved. Oak gene expression patterns diverged markedly during development of galled and normal buds. Young galls showed elevated expression of oak genes similar to legume root nodule Nod factor-induced early nodulin (ENOD) genes and developmental parallels with oak buds. In contrast, mature galls showed substantially different patterns of gene expression to mature leaves. While most oak transcripts could be functionally annotated, many gall wasp transcripts of interest were novel. We found no evidence in the gall wasp for involvement of third-party symbionts in gall induction, for effector delivery using virus-like-particles, or for gallwasp expression of genes coding for plant hormones. Many differentially and highly expressed genes in young larvae encoded secretory peptides, which we hypothesise are effector proteins exported to plant tissues. Specifically, we propose that host arabinogalactan proteins and gall wasp chitinases interact in young galls to generate a somatic embryogenesis-like process in oak tissues surrounding the gall wasp larvae. Gall wasp larvae also expressed genes encoding multiple plant cell wall degrading enzymes (PCWDEs). These have functional orthologues in other gall inducing cynipids but not in figitid parasitoid sister groups, suggesting that they may be evolutionary innovations associated with cynipid gall induction.

Phylogeny and systematic revision of the helicarionid semislugs of eastern Queensland (Stylommatophora, Helicarionidae)

The helicarionid fauna of southeastern to mid-eastern Queensland is dominated by a group of semislugs with moderately reduced shells belonging to genera Fastosarion, Eungarion, Stanisicarion, Dimidarion, Macularion and Hymanarion. We comprehensively revise their systematic classification using comparative morpho-anatomy and mitochondrial phylogenetics, and demonstrate that these genera combined form a well-differentiated and monophyletic radiation. In our mitochondrial phylogeny, this radiation is divided into three main clades that are statistically well supported. One clade is also well defined in terms of diagnostic morpho-anatomical characters, but we could not identify diagnostic characters for the other two clades due to considerable levels of morpho-anatomical variation. We propose accepting only two genera, Fastosarion (with junior synonyms Eungarion, Dimidarion, and Hymanarion) and Stanisicarion (with junior synonym Macularion). Both genera represent mutually monophleytic sister taxa that can consistently be distinguished by the presence or absence of a penial verge that is fused to the penial wall and by egg shape. We also synonymise Fastosarion ameyi with F. aquavitae, F. schelli with F. helenkingae, Dimidarion peterbrocki and D. slatyeri with F. alyssa, Stanisicarion virens with S. freycineti. Revised species descriptions are presented for Fastosarion alyssa, F. aquavitae, F. brazieri, F. comerfordae, F. griseolus, F. hannianus, F. helenkingae, F. mcdonaldi, F. minerva, F. paluma, F. papillosus, F. pustulosus, F. superbus, Stanisicarion aquila and S. freycineti. Nine new species, Fastosarion deensis, F. ephelis, F. insularis, F. katatonos, F. longimentula, F. rowani, F. sarina, F. tuljun and Stanisicarion wolvi are described, bringing the total number of accepted species to 24.

Pollination Syndromes of Chinese Gesneriaceae: a Comparative Study between Hainan Island and Neighboring Regions

The species-rich Gesneriaceae are typically a tropical family in Asia, showing a monophyletic radiation and high endemism in Southwest China and Hainan Island. The Chinese species have diverse floral traits and pollination systems, but the detailed patterns of diversity and possible differentiations between Hainan Island and the Chinese mainland remain unclear. Here, we enumerate the species diversity and proportion of endemics of Gesneriaceae for Hainan Island and the nearby Chinese provinces of Yunnan, Guangxi, Guizhou, and Guangdong. We then investigate the species evolutionary histories and main floral traits to evaluate speciation and pollination syndromes for the island and mainland flora. We recognize 24 (eight endemic) species on Hainan Island, 236 (106 endemic) in Yunnan, 211 (120 endemic) in Guangxi, 97 (28 endemic) in Guizhou, and 60 (20 endemic) in Guangdong. Although Hainan Island harbors fewer species than nearby regions, probably due to its smaller area, its endemic ratio is high, only slightly lower than Guangxi. A phylogenetic tree based on nuclear ITS 1/2 and chloroplast Trn L-F indicated most Hainan-endemic species were genetically close to species from Southeast Asia, rather than mainland China. For most floral traits, e.g., growth form, corolla type and color, Hainan Island species show no differences from other regions. Hainan Island and Yunnan Province have equal proportions of species with four or two stamens, whereas most species in other regions have two stamens. Hainan Island has a much higher percentage (21%) of actinomorphic species than other regions (< 10%). Most species in Hainan Island have exserted stamens, while stamens are included in most species in other regions. We did not find any increased tendency in floral traits that promote selfing for the island flora. Generalist pollination mechanisms, supported by characters such as actinomorphic corolla, appear to provide sufficient reproductive assurance in pollinator-depauperate Hainan Island.

Molecular phylogenetics and systematic revision of the south-eastern Australian Helicarionidae (Gastropoda, Stylommatophora)

The south-eastern Australian helicarionid clade currently comprises six genera of snails and semislugs united by genital characters, including an epiphallic flagellum that produces a spiraling, spinose spermatophore, the absence of an epiphallic caecum, and the presence of at most a very short vagina. We comprehensively revise the taxonomy of this group based on comparative analyses of key morphological features and mitochondrial markers COI and 16S, revise the placement of several species described recently on the basis of shell morphology alone, and describe new taxa. The snail genus Brevisentis is monophyletic as currently understood, but includes an additional undescribed species from Wollemi National Park, New South Wales. Mysticarion is shown to contain four arboreal semislugs with wide, disjunct ranges, including one new species (Mysticarion obscurior sp. nov.). We synonymise Fastosarion staffordorum with Mysticarion hyalinus. The semislug Desidarion is synonymised with Parmavitrina, and we describe two new species of this genus, P. flavocarinata sp. nov. and P. maculosa sp. nov. The semi-arboreal semislug Cucullarion is herein included in the south-eastern Australian helicarionid clade based on morphological and genetic evidence, despite its more northerly distribution. Two small semislugs so far placed in Peloparion do not group together and a new genus, Ubiquitarion gen. nov., is described for Peloparion iridis. All of these genera, together with the semislug Helicarion (not included here), form a monophyletic radiation endemic to southeastern Australia.

Multiple colonisations of the Lake Malawi catchment by the genus Opsaridium (Teleostei: Cyprinidae)

It has been proposed that the fish faunas of African rivers assemble through multiple colonisation events, while lake faunas form additionally through intralacustine speciation. While this pattern has been established for many lineages, most notably cichlids, there are opportunities to further investigate the concept using phylogenies of congeneric endemic species within ancient lake catchments. The Lake Malawi catchment contains three river-spawning cyprinids of the genus Opsaridium, two of which are endemic. These species differ in body size, migratory behaviour and habitat use, but it has never previously been tested if these represent a monophyletic radiation, or have instead colonised the lake independently. We placed these species in a broader phylogeny of Opsaridium and the related genus Raiamas, including all known species from the river systems surrounding Lake Malawi. Our results suggest that each of the species has independently colonised the lake catchment, with all three taxa having well-defined sister taxa outside of the lake, and all sharing a common ancestor ∼14.9million years ago, before the Lake Malawi basin started to form ∼8.6million years ago. Additionally, the results strongly support previous observations that Opsaridium is not a monophyletic group, but instead contains Raiamas from the Congo drainage. Together these results are supportive of the concept that river fish faunas within African catchments are primarily assembled through a process of accumulation from independent origins, rather than within-catchment speciation and adaptive radiation. In light of these results we also suggest there is scope for a re-evaluation of systematics of both Opsaridium and Raiamas.

Ecological specialization and morphological diversification in Greater Antillean boas.

Colonization of islands can dramatically influence the evolutionary trajectories of organisms, with both deterministic and stochastic processes driving adaptation and diversification. Some island colonists evolve extremely large or small body sizes, presumably in response to unique ecological circumstances present on islands. One example of this phenomenon, the Greater Antillean boas, includes both small (<90 cm) and large (4 m) species occurring on the Greater Antilles and Bahamas, with some islands supporting pairs or trios of body-size divergent species. These boas have been shown to comprise a monophyletic radiation arising from a Miocene dispersal event to the Greater Antilles, though it is not known whether co-occurrence of small and large species is a result of dispersal or in situ evolution. Here, we provide the first comprehensive species phylogeny for this clade combined with morphometric and ecological data to show that small body size evolved repeatedly on separate islands in association with specialization in substrate use. Our results further suggest that microhabitat specialization is linked to increased rates of head shape diversification among specialists. Our findings show that ecological specialization following island colonization promotes morphological diversity through deterministic body size evolution and cranial morphological diversification that is contingent on island- and species-specific factors.

The Retina of Ansorge's Cusimanse (Crossarchus ansorgei): Number, Topography and Convergence of Photoreceptors and Ganglion Cells in Relation to Ecology and Behavior

The family Herpestidae (cusimanses and mongooses) is a monophyletic radiation of carnivores with remarkable variation in microhabitat occupation and diel activity, but virtually nothing is known about how they use vision in the context of their behavioral ecology. In this paper, we measured the number and topographic distribution of neurons (rods, cones and retinal ganglion cells) and estimated the spatial resolving power of the eye of the diurnal, forest-dwelling Ansorge's cusimanse (Crossarchus ansorgei). Using retinal wholemounts and stereology, we found that rods are more numerous (42,500,000; 92%) than cones (3,900,000; 8%). Rod densities form a concentric and dorsotemporally asymmetric plateau that matches the location and shape of a bright yellow tapetum lucidum located within the dorsal aspect of the eye. Maximum rod density (340,300 cells/mm²) occurs within an elongated plateau below the optic disc that corresponds to a transitional region between the tapetum lucidum and the pigmented choroid. Cone densities form a temporal area with a peak density of 44,500 cells/mm² embedded in a weak horizontal streak that matches the topographic distribution of retinal ganglion cells. Convergence ratios of cones to retinal ganglion cells vary from 50:1 in the far periphery to 3:1 in the temporal area. With a ganglion cell peak density of 13,400 cells/mm² and an eye size of 11 mm in axial length, we estimated upper limits of spatial resolution of 7.5-8 cycles/degree, which is comparable to other carnivores such as hyenas. In conclusion, we suggest that the topographic retinal traits described for Ansorge's cusimanse conform to a presumed carnivore retinal blueprint but also show variations that reflect its specific ecological needs.