Independent evolutionary reductions of the phallus in basal birds

Despite a long history of anatomical studies in birds, the genitalia of most avian species remain undescribed. Birds are the only vertebrate taxon with internal fertilization where an intromittent phallus has been lost in most species. Studying the anatomical transitions of the avian phallus in those species where it is still present, allows us to test evolutionary hypotheses of why the phallus was lost in the ancestor of modern birds. As part of an anatomical survey of the evolution of avian phallus morphology, we have examined some avian species whose genitalia have not been described. Previously, there were only two known events of phallus reduction in birds: one transition from intromittent to non‐intromittent in the Galliformes, and a complete loss of phallic structures in the ancestor of Neoaves. Here we report three additional cases of phallus reduction in birds: a transition from intromittent to non‐intromittent phallus in Tinamiformes (Crypturellus, Tinamidae), the presence of a non‐intromittent phallus in Alectura (Megapodidae), and a complete loss of the phallus in Leipoa (Megapodidae). In addition, we report on the unique morphology of the Crypturellus non‐intromittent phallus. These new records of phallus reduction highlight the dynamic nature of phallus evolution in birds. Our findings provide evidence against the hypothesis that the phallus in birds is maintained to insure paternity in taxa with exclusive male parental care, since both groups where we report phallus reduction provide predominately male‐only care.     

The evolution of Zoraptera

Zoraptera is one of the most enigmatic and least understood orders in insects. Based on a wide taxon sampling from all continents where the group is known, we applied a phylogenetic approach using multiple DNA sequences to elucidate species-level relationships. The resulting phylogeny shows that Zoraptera is divided into three major clades, and that two comprise species distributed on different continents. The monophyly of these clades is at least partly supported by shared derived morphological features. The divergence age estimation and ancestral distribution area reconstruction suggest an ancient origin and early radiation initiated in the Permian. Plate tectonics theory suggests that the present distribution of Zoraptera was mainly established by vicariance, rather than dispersal. The three major clades probably originated on the Pangaea supercontinent, or alternatively on the linked Gondwana and Laurasia supercontinents. Their ancient origin explains previously found conspicuous interspecific variation of the genital apparatus, sperm structure and mating behaviour, in striking contrast to a highly conserved general body morphology. We compiled data of available reproductive features and reconstructed the character evolution. Our analyses revealed repeated acquisitions and/or losses of a hyperelongated intromittent organ, mating hooks and tergal protuberances.     

Geophilomorph centipedes from the Cretaceous amber of Burma

The only previously known Mesozoic fossils of the chilopod order Geophilomorpha are two species from the Late Jurassic and Late Cretaceous, both known from single specimens that cannot be assigned with precision to a family. Four specimens from the Late Cretaceous (earliest Cenomanian) amber of Burma include three that can be identified as conspecific, described here as Kachinophilus pereirai gen. nov. sp. nov. These specimens preserve greater morphological detail in comparison with other fossil geophilomorphs: the form and fine features of the head, the maxillary complex, the trunk sternites with associated glandular pores and the ultimate pair of legs defend the assignment of the species to the extant family Geophilidae, and most probably to a derived subgroup including well‐known extant genera such as Ribautia Brölemann, 1909. Confocal laser scanning microscopy supplements examination under incident and transmitted light to document details of high taxonomic relevance in the head and the forcipular segment. The modern appearance of this species and its membership among deeply nested extant clades are consistent with molecular estimates that most of the diversity of crown‐group Geophilomorpha originated before the Late Cretaceous.     

Ovoviviparity and genital evolution: a lesson from an earwig species with coercive traumatic mating and accidental breakage of elongated intromittent organs

Ovoviviparity or viviparity has evolved independently in animals and involves adaptations in females to accommodate developing embryos for a prolonged duration in their bodies, a condition which has likely to have influenced the evolution of the male genitalia. We aimed to ascertain whether the elongated male genitalia of the ovoviviparous free‐living earwig species Marava arachidis (Dermaptera: Spongiphoridae) delivers sperm directly to the female ovaries where fertilization occurs. Males mated coercively with females by grabbing the female antenna with their mouth parts. Although females resisted the mating attempts, pairs mated 3.3 times on average over 15 h. The elongated intromittent organ, known as a virga, was inserted into the long‐tubed spermatheca during insemination. Surgical ectomy of the spermatheca confirmed that sperm migrated from here to the ovaries with a variable delay. A pair of sclerites in the male genitalia frequently inflicted wounds near the spermathecal opening, while the single, thin virga sometimes broke off during mating. However, unlike earwigs bearing a ‘spare’ virga, damage was restricted to the tip of the virga, without which the males could still inseminate the females. We discuss the evolution of the genitalia in this insect in the light of sexual selection and sexual conflict over mating and fertilization.     

Phenotypic and genetic variation in male genitalia in the seedbug, Lygaeus equestris (Heteroptera)

Male genitalia evolve through sexual selection and, in insects, tend to show negative static allometry, low phenotypic variation, and are usually relatively small. Much less is known about the genetic variation and heritability of male genitalia. Additionally, in instances where the intromittent organ is greatly elongated, it is unclear whether typical patterns of genital scaling and variation also apply. In the present study, we investigated the allometry, variation, and heritability of male genital length in the seedbug, Lygaeus equestris , a species with a greatly elongated intromittent organ (i.e. almost as long as male body size). We found that genital length was negatively allometric, in spite of its great length, and was no more variable than nongenital traits. Additionally, genital length was significantly heritable and had considerable evolvability.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 400–405.     

An enigmatic lineage of mites from Baltic amber shows a unique,possibly female‐controlled,mating

It is generally assumed that male control over mating and a lack of precopulatory female choice are prevalent in many animals and in astigmatan mites in particular. We show that several morphological structures of females of some astigmatan mites are indicative of precopulatory female choice: (1) copulatory tubes acting like intromittent organs; (2) specialized structures assisting male–female attachment and possibly allowing indirect mate selection in immature females; and (3) a unique, pad‐like terminal opisthosomal organ used to cling to the male during copulation in Glaesacarus rhombeus (= Acarus rhombeus Koch et Berendt, 1854) belonging to an extinct family, Glaesacaridae, from the Upper Eocene Baltic amber. An exceptionally well‐preserved copulating pair from amber provides insight into the function of this organ and reproductive behaviour in this mite. Female control over mating may reduce the timing of insemination, harassment by males, and damage caused by copulation. As a consequence, this can lessen male–male aggression, select against precopulatory guarding, and reduce the risk of predation. By contrast to extant taxa, males of G. rhombeus do not have any apparent specialized structures aiding clinging to the female during copulation, suggesting that this mating system is either an earlier step in the evolution of the female‐dominated mating system and/or a remarkable example of imbalanced female counteradaptations against the male's reproductive interest that may occur during an arms race between the two sexes. We offer an approach that can falsify the hypothesis assuming precopulatory female choice and discuss an alternative hypothesis suggesting that these female structures evolved in response to the need to reduce damage associated with mating or precopulatory guarding. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 661–668.     

Early evolution of Cupedidae revealed by a mid‐Cretaceous reticulated beetle from Myanmar (Coleoptera: Archostemata)

Cupedidae, the most species‐rich family of the archaic suborder Archostemata, were abundant, diverse and widespread in the Mesozoic, yet little is known about the early evolution and biogeography. This stems, in part, from a lack of exceptionally preserved fossils from the Mesozoic and of formal phylogenetic study of both extant and extinct taxa. Here we describe and illustrate a new fossil from mid‐Cretaceous Burmese amber, and provide a phylogeny combining both fossils and all known extant genera of Archostemata. A dataset of 43 ingroup taxa and four outgroup taxa based on 110 morphological characters was analysed under parsimony. The results indicate that Priacma LeConte and Paracupes Kolbe, as well as the Cretaceous genera Barbaticupes Jarzembowski et al. and Mallecupes Jarzembowski et al., together form a sister clade to the rest of Cupedidae. Priacma megapuncta sp.n. is attributed to the relict North American Priacma by the presence of distinct subtruncate elytral apices, lateral elytral margins with two rows of sharp teeth, and peculiar fixing epipleural folds near the elytral apices. Our discovery of the first fossil species of Priacma in Burmese amber reveals the antiquity and wider distribution of the genus in the late Mesozoic. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:313565C2‐4F42‐48BD‐8720‐F379DE202868 .     

One tool, many uses: precopulatory sexual selection on genital morphology in Aquarius remigis

While congruent evidence indicates that sexual selection is the most likely selective force explaining the rapid divergence of male genital morphology in insects, the mechanisms involved in this process remain unclear. In particular, little attention has been paid to precopulatory sexual selection. We examine sexual selection for mating success on male genital components in six populations of Aquarius remigis, a water strider characterized by unique genital morphology. Multivariate selection analysis confirms previous findings that precopulatory sexual selection favours longer external genitalia, and provides new evidence that this selection acts independently on external genital components. In contrast, the size of the major internal genital sclerite is not correlated with mating success. Thus, precopulatory sexual selection acts strongly on the size of the external genitalia, but not on the intromittent organ itself. These results highlight the multiple functions of genital organs and the importance of both precopulatory and post-copulatory sexual selection in shaping the remarkable diversity of male genitalia in insects.     

The past and the present through phylogenetic analysis: the rove beetle tribe Othiini now and 99 Ma

In order to classify and taxonomically describe the first two fossil Othiini (Coleoptera: Staphylinidae: Staphylininae) species from three well‐preserved specimens in Cretaceous Burmese amber, a phylogenetic analysis was conducted, combining extant and extinct taxa. A dataset of 76 morphological characters scored for 33 recent species across the subfamilies Staphylininae and Paederinae was analysed using maximum parsimony and Bayesian inference methods. The many differing phylogenetic hypotheses for higher‐level relationships in the large rove beetle subfamilies Staphylininae and Paederinae were summarized and their hitherto known fossil record was reviewed. Based on the analyses, the new extinct genus Vetatrecus gen.n. is described with two new species: V. adelfiae sp.n. and V. secretum sp.n. Both species share character states that easily distinguish them from all recent Othiini and demonstrate a missing morphological link between subfamilies Staphylininae and Paederinae. This is the first morphology‐based evidence for the paraphyly of Staphylininae with respect to Paederinae, suggested earlier by two independent molecular‐based phylogenies of recent taxa. Our newly discovered stem lineage of Othiini stresses the importance of fossils in phylogenetic analyses conducted with the aim of improving the natural classification of extant species. It also suggests that the definitions of Staphylininae and Paederinae, long‐established family‐group taxa, may have to be reconsidered. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:817F39C4-F36B-4FD9-96CD-5F8FB064C39E .     

Inferring social behavior from sexual dimorphism in the fossil record

Sexual dimorphism is commonly used as evidence of the behavior of extinct species. Even so, few analyses scrutinize whether extant comparative data support inferences of mating systems or behavior in extinct species. This analysis evaluates the relations between measures of dimorphism and several estimates of mating system and intrasexual competition. Dimorphism alone provides poor resolution for reconstructing behavior. Many behavioral inferences based on perceived dimorphism are not supported by extant comparative data. This reflects the large standard errors of relations between dimorphism estimates and behavioral classifications. Used with caution, dimorphism can provide a hint of the behavior of extinct species in some cases. However, in many cases inferred dimorphism allows little more than an inference of polygyny, without any indication of specific types of mating systems.     

The earliest Timematids in Burmese amber reveal diverse tarsal pads of stick insects in the mid‐Cretaceous

Many extant insects have developed pad structures, euplantulae or arolia on their tarsi to increase friction or enhance adhesion for better mobility. Many polyneopteran insects with euplantulae, for example, Grylloblattodea, Mantophasmatodea and Orthoptera, have been described from the Mesozoic. However, the origin and evolution of stick insects' euplantulae are poorly understood due to rare fossil records. Here, we report the earliest fossil records of Timematodea hitherto, Tumefactipes prolongates gen. et sp. nov. and Granosicorpes Urates gen. et sp. nov., based on three specimens from mid-Cretaceous Burmese amber. Specimens of Tumefactipes prolongates gen. et sp. nov. have extremely specialized and expanded euplantulae on their tarsomere II. These new findings are the first known and the earliest fossil records about euplantula structure within Phasmatodea, demonstrating the diversity of euplantulae in Polyneoptera during the Mesozoic. Such tarsal pads might have increased friction and helped these mid-Cretaceous stick insects to climb more firmly on various surfaces, such as broad leaves, wetted tree branches or ground. These specimens provide more morphological data for us to understand the relationships of Timematodea, Euphasmatodea, Orthoptera and Embioptera, suggesting that Timematodea might be monophyletic with Euphasmatodea rather than Embioptera and Phasmatodea should have a closer relationship with Orthoptera rather than Embioptera.     

Two intromittent organs in Zorotypus caudelli (Insecta,Zoraptera): the paradoxical coexistence of an extremely long tube and a large spermatophore

Very unusual genitalia of the species Zorotypus caudelli are described. It contains the unique configuration of two different intromittent organs, one of them strongly elongated. Hyper elongated genitalia are known in different groups of insects. Males have to accommodate these unwieldy structures in the limited spaces of the abdomen and manipulate them acutely during copulation. A crucial question is how do species with elongated genitalia cope with these requirements? To investigate this, we studied key features enabling storage, insertion, and withdrawal of the elongated genitalia. The co‐existence of an elongated narrow tube and a bulky spermatophore is a highly unusual and apparently paradoxical condition. However, we demonstrate that the tube is not involved in sperm transmission, whereas the large spermatophore is transferred to females by a membranous fold of the genitalia. The movement of the spermatophore is caused by haemolymph pressure, which likely also promotes the insertion of both intromittent organs. A comparison with the genital anatomy and reproductive mode in related groups suggests that the elongated tube and its accommodating pouch is a de novo structure, and that the ancestral sperm transport via spermatophore is a preadaptive condition for the acquisition of this unusual structure. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 40–54.     

Phylogeny of the rove beetle tribe Gymnusini sensu n. (Coleoptera: Staphylinidae: Aleocharinae): implications for the early branching events of the subfamily

The rove beetle subfamily Aleocharinae is the largest subfamily of animals known in terms of species richness. Two small aleocharine tribes, Gymnusini and Deinopsini, are believed to be a monophyletic clade, sister to the rest of the Aleocharinae. Although the phylogenetic relationships of the extant lineages have been well investigated, the monophyly of Gymnusini has been questioned due to a series of previous studies and the recent discovery of the aleocharine †Cretodeinopsis Cai & Huang (Deinopsini) from mid‐Cretaceous Burmese amber. Using an additional specimen of †Cretodeinopsis and well‐preserved specimens of †Electrogymnusa Wolf‐Schwenninger from Eocene Baltic amber, we present here two types of morphology‐based phylogenetic analyses, employing all extant/extinct genera of Gymnusini and Deinopsini for the first time. The maximum parsimony and Bayesian analyses recovered a monophyletic clade of the two tribes combined, but each analysis suggested nonmonophyly of Gymnusini. In agreement with the results of the present study, we synonymize Deinopsini syn.n. under Gymnusini sensu n. , by priority. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:F09EB444‐C6CA‐4525‐A986‐3CFC826F5877 .     

Systematics and evolution of the Pan‐Alcidae (Aves,Charadriiformes)

Puffins, auks and their allies in the wing‐propelled diving seabird clade Pan‐Alcidae (Charadriiformes) have been proposed to be key pelagic indicators of faunal shifts in Northern Hemisphere oceans. However, most previous phylogenetic analyses of the clade have focused only on the 23 extant alcid species. Here we undertake a combined phylogenetic analysis of all previously published molecular sequence data (～ 12 kb) and morphological data (n = 353 characters) with dense species level sampling that also includes 28 extinct taxa. We present a new estimate of the patterns of diversification in the clade based on divergence time estimates that include a previously vetted set of twelve fossil calibrations. The resultant time trees are also used in the evaluation of previously hypothesized paleoclimatic drivers of pan‐alcid evolution. Our divergence dating results estimate the split of Alcidae from its sister taxon Stercorariidae during the late Eocene (～ 35 Ma), an evolutionary hypothesis for clade origination that agrees with the fossil record and that does not require the inference of extensive ghost lineages. The extant dovekie Alle alle is identified as the sole extant member of a clade including four extinct Miocene species. Furthermore, whereas an Uria + Alle clade has been previously recovered from molecular analyses, the extinct diversity of closely related Miocepphus species yields morphological support for this clade. Our results suggest that extant alcid diversity is a function of Miocene diversification and differential extinction at the Pliocene–Pleistocene boundary. The relative timing of the Middle Miocene climatic optimum and the Pliocene–Pleistocene climatic transition and major diversification and extinction events in Pan‐Alcidae, respectively, are consistent with a potential link between major paleoclimatic events and pan‐alcid cladogenesis.     

Mating behavior and the function of the male genital spine in the ground beetle Carabus clathratus

The morphologies of male genitalia often appear harmful or aggressive, as if they may inflict physical damage upon females during copulation. Such male genitalia are often thought to function in intra- and intersexual interactions during mating. In the carabid genus Carabus, division Spinulati, males possess a spine (spinula) on the intromittent organ, of which function is unknown. To reveal the function of the spinula, we studied the mating behavior and genital coupling of a Spinulati species, Carabus (Limnocarabus) clathratus. The males positioned the spinula along the inner wall of the vaginal opening throughout copulation. This placement created a small dent and subsequently a melanized patch (wound) on the vaginal wall, but the spinula rarely penetrated the vaginal wall. The spinula did not reach the innermost part of the vagina where the spermatophore is deposited. These results suggest that the spinula is not used for inflicting damage on female genitalia or manipulating spermatophores of rival males. During spermatophore formation, the male partially withdrew the aedeagus, and only the aedeagal tip and endophallus remained within the female. By placing the spinula against the vaginal wall, the male could hold the endophallus within the vaginal chamber in the unstable copulatory posture. Thus, our observations suggest that the spinula primarily functions as an "anchor" to maintain the coupling of the male and female genitalia and thereby ensure insemination.     

The first Ironomyiidae from mid‐Cretaceous Burmese amber provides insights into the phylogeny of Phoroidea (Diptera: Cyclorrhapha)

Macalpinomyia jiewenae gen. et sp.n. is described from the mid‐Cretaceous (～99 Ma) amber of Myanmar. Macalpinomyia jiewenae is the first Oriental representative of the enigmatic family Ironomyiidae (Diptera: Phoroidea), currently known from a single extant genus restricted to southeastern Australia, plus a monotypic genus from Canadian amber and three controversial genera based on impression fossils from China, Mongolia and Russia. A phylogenetic analysis of all Phoroidea families, including all ironomyiid extant and extinct genera, corroborates the monophyly of Ironomyiidae, and Macalpinomyia gen.n. is assigned to the subfamily Sinolestinae. Cretonomyiinae subfam.n. , is erected to accommodate the basal lineage of Ironomyiidae. Lebambromyia acrai Grimaldi & Cumming, previously placed in Ironomyiidae, is supported as an early branching lineage of Platypezidae. Our topology proposes that Ironomyiidae is sister to the remaining Phoroidea. The phylogenetic results, in combination with the fossil ages and relevant molecular divergence time analysis, suggests that Ironomyiidae probably originated at least in the Berriasian of the Early Cretaceous (～140 Ma). This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:5DFFC944‐1350‐418E‐BCDC‐BB87FC013D5D .     

Microsatellite markers developed using a next‐generation sequencing technique for Neotrogla spp. (Psocodea: Prionoglarididae), cave dwelling insects with sex‐reversed genitalia

The genus Neotrogla (Psocodea: Prinoglarididae) comprises four named species from Brazil. Females of this cave‐dwelling insect are characterized by a conspicuous penis‐like intromittent organ, termed a gynosome, which is inserted into the vagina‐like male genitalia during copulation. Another evolutionarily novel structure, the spermathecal plate, enables a female to simultaneously store two freshly deposited spermatophores (consisting of sperm and possibly nutritious substances) in her sperm storage organ (spermatheca). It is unknown whether the two spermatophores are derived from two different males. To investigate the mating ecology and population genetic structures of these insects with sex‐reversed genitalia, 16 novel highly polymorphic microsatellite loci were isolated and characterized based on ~2,275 Mbp genomic sequences from an undescribed Neotrogla species. Our first screening detected 99,888 candidate loci. Similar to other hemipteroid insects studied thus far, AAT motif microsatellites were conspicuously dominant. We further screened 99 sequences, for which 50 pairs of polymerase chain reaction primers were successfully designed. Sixteen of these primers successfully amplified products of the expected size in the 11 Neotrogla sp. individuals collected from two caves. The number of alleles per loci varied from two to nine, with no significant deviation from the Hardy–Weinberg equilibrium in either population. Although the caves sampled were only approximately 1 km apart, significant genetic differentiation was detected between the two populations. In total, 13, 12, 13 and 11 loci were cross‐amplified in N. aurora, N. brasiliensis, N. curvata and N. truncata, respectively, indicating the applicability of these microsatellite loci for metapopulation genetic studies in multiple Neotrogla species.     

On the relationship between hypsodonty and feeding ecology in ungulate mammals,and its utility in palaeoecology

High‐crowned (hypsodont) teeth are widely found among both extant and extinct mammalian herbivores. Extant grazing ungulates (hoofed mammals) have hypsodont teeth (a derived condition), and so extinct hypsodont forms have usually been presumed to have been grazers. Thus, hypsodonty among ungulates has, over the past 150 years, formed the basis of widespread palaeoecological interpretations, and has figured prominently in the evolutionary study of the spread of grasslands in the mid Cenozoic. However, perceived inconsistencies between levels of hypsodonty and dental wear patterns in both extant and extinct ungulates have caused some workers to reject hypsodonty as a useful predictive tool in palaeobiology, a view that we consider both misguided and premature. Despite the acknowledged association between grazing and hypsodonty, the quantitative relationship of hypsodonty to the known ecology of living ungulate species, critical in making interpretations of the fossil record, was little studied until the past two decades. Also, much of the literature on ungulate ecology relevant to understanding hypsodonty has yet to be fully incorporated into the perspectives of palaeontologists. Here we review the history and current state of our knowledge of the relationship between hypsodonty and ungulate ecology, and reassert the value of hypsodonty for our understanding of ungulate feeding behaviour. We also show how soil consumption, rather than the consumption of grass plants per se, may be the missing piece of the puzzle in understanding the observed correlation between diets, habitats, and hypsodonty in ungulates. Additionally, we show how hypsodonty may impact life‐history strategies, and resolve some controversies regarding the relevance of hypsodonty to the prediction of the diets of extinct species. This in turn strengthens the utility of hypsodonty in the determination of past environmental conditions, and we provide a revised view of a traditional example of evolutionary trends in palaeobiology, that of the evolution of hypsodonty in horses and its correlation with the Miocene spread of grasslands in North America.