Interspecific Mating Research Articles

Correlated evolution of self and interspecific incompatibility across the range of a Texas wildflower.

Selection to prevent interspecific mating can cause an increase or a decrease in self-pollination in sympatric populations. Characterizing the geographical variation in self and interspecific incompatibilities within a species can reveal if and how the evolution of self and interspecific mate choice are linked. We used controlled pollinations to characterize the variation in self and interspecific incompatibility across 29 populations of Phlox drummondii. We evaluated seed set from these pollinations and described the developmental timing of variation in pollen-pistil compatibility. There is extensive quantitative variation in self-incompatibility and interspecific-incompatibility with its close congener P.cuspidata. Phlox drummondii populations that co-occur and hybridize with P.cuspidata have significantly higher interspecific incompatibility and self-incompatibility than geographically isolated P.drummondii populations. The strength of self and interspecific incompatibility is significantly correlated among individuals and the strength of both incompatibilities is explained by the success of pollen adhesion to the stigma. The correlated strength of self and interspecific incompatibility across the range of P.drummondii and the concurrent developmental timing of the pollen-pistil interaction, suggests these incompatibilities have an overlapping molecular mechanism. The geographical distribution of variation in incompatibilities indicates that this mechanistic link between incompatibilities may affect the evolution of mate choice in plants.

Reproductive Costs for Hybridizing Female Anasa tristis (Hemiptera: Coreidae), but No Evidence of Selection Against Interspecific Mating.

Individuals of different species sometimes mate in nature, and such behavior often carries costs, such as wasted gametes and inviable offspring. One context in which interspecific mating commonly occurs is when closely related species come into secondary contact. Here, we tested whether reproductive isolation is greater in an area of recent secondary contact than in allopatry for two closely related insect species, and we examined whether mating between individuals of these two species constitutes reproductive interference. In Florida, two species of squash bugs (Hemiptera: Coreidae: Anasa tristis DeGeer and Anasa andresii Guérin-Méneville) have been secondarily sympatric for ≥80 generations, and male A. andresii copulate with female A. tristis. Because hybridization is often costly for females, we predicted that secondarily sympatric females would be less likely to mate with heterospecifics than would allopatric females. We found no evidence of recent selection on reproductive isolation: females from both populations were equally likely to mate with heterospecifics, and heterospecific males did not make more mating attempts than conspecifics to achieve copulations. However, female A. tristis paired with heterospecifics produced many fewer eggs and offspring than females paired with conspecifics, and this did not differ according to whether females were from allopatric or sympatric populations. Our findings show that reproductive barriers between these species existed before secondary contact. We suggest that habitat use may limit encounter frequency, and that female choice, multiple mating, and postcopulatory processes may reduce costs for females. Consequently, we suggest that mating systems and ecological factors mediate the effects of reproductive interference.

Inter-specific courtship and mating in butterflies of the genus Pieris Schrank, 1801 (Lepidoptera: Pieridae)

Inter-specific courtship and mating in butterflies of the genus Pieris Schrank, 1801 (Lepidoptera: Pieridae)

Unravelling species boundaries in the Aspergillus viridinutans complex (section Fumigati): opportunistic human and animal pathogens capable of interspecific hybridization.

Although Aspergillus fumigatus is the major agent of invasive aspergillosis, an increasing number of infections are caused by its cryptic species, especially A. lentulus and the A. viridinutans species complex (AVSC). Their identification is clinically relevant because of antifungal drug resistance and refractory infections. Species boundaries in the AVSC are unresolved since most species have uniform morphology and produce interspecific hybrids in vitro. Clinical and environmental strains from six continents (n = 110) were characterized by DNA sequencing of four to six loci. Biological compatibilities were tested within and between major phylogenetic clades, and ascospore morphology was characterised. Species delimitation methods based on the multispecies coalescent model (MSC) supported recognition of ten species including one new species. Four species are confirmed opportunistic pathogens; A. udagawae followed by A. felis and A. pseudoviridinutans are known from opportunistic human infections, while A. felis followed by A. udagawae and A. wyomingensis are agents of feline sino-orbital aspergillosis. Recently described human-pathogenic species A. parafelis and A. pseudofelis are synonymized with A. felis and an epitype is designated for A. udagawae. Intraspecific mating assay showed that only a few of the heterothallic species can readily generate sexual morphs in vitro. Interspecific mating assays revealed that five different species combinations were biologically compatible. Hybrid ascospores had atypical surface ornamentation and significantly different dimensions compared to parental species. This suggests that species limits in the AVSC are maintained by both pre- and post-zygotic barriers and these species display a great potential for rapid adaptation and modulation of virulence. This study highlights that a sufficient number of strains representing genetic diversity within a species is essential for meaningful species boundaries delimitation in cryptic species complexes. MSC-based delimitation methods are robust and suitable tools for evaluation of boundaries between these species.

Light is required for proper female mate choice between winged and wingless males in Drosophila.

In many animal species, females choose potential mating partners according to their own preferences. Thus, female preference-based mate choice affects intraspecific mating success and prevents interspecific mating. To clarify the neuronal basis of female mate choice, it is essential to identify the important relevant sensory cues. In the fruitfly Drosophila melanogaster, the courtship song of males promotes female sexual receptivity. When wild-type virgin females can freely choose one of two types of courting males (winged or wingless males), they prefer to mate with winged males. Here, we report a crucial sensory cue relevant to this female mate choice. In a female choice test, female receptivity toward winged and wingless males was markedly reduced when females had auditory impairments, although females with visual or olfactory impairments showed normal receptivity similar to wild-type females. However, females with visual impairments did not show clear mate preference toward winged males. Thus, these findings suggest that females utilize visual cues in mate choice between winged and wingless males in Drosophila.

Molecular evidence of hybridization in sympatric populations of the Enantia jethys complex (Lepidoptera: Pieridae).

Hybridization events are frequently demonstrated in natural butterfly populations. One interesting butterfly complex species is the Enantia jethys complex that has been studied for over a century; many debates exist regarding the species composition of this complex. Currently, three species that live sympatrically in the Gulf slope of Mexico (Enantia jethys, E. mazai, and E. albania) are recognized in this complex (based on morphological and molecular studies). Where these species live in sympatry, some cases of interspecific mating have been observed, suggesting hybridization events. Considering this, we employed a multilocus approach (analyses of mitochondrial and nuclear sequences: COI, RpS5, and Wg; and nuclear dominant markers: inter-simple sequence repeat (ISSRs) to study hybridization in sympatric populations from Veracruz, Mexico. Genetic diversity parameters were determined for all molecular markers, and species identification was assessed by different methods such as analyses of molecular variance (AMOVA), clustering, principal coordinate analysis (PCoA), gene flow, and PhiPT parameters. ISSR molecular markers were used for a more profound study of hybridization process. Although species of the Enantia jethys complex have a low dispersal capacity, we observed high genetic diversity, probably reflecting a high density of individuals locally. ISSR markers provided evidence of a contemporary hybridization process, detecting a high number of hybrids (from 17% to 53%) with significant differences in genetic diversity. Furthermore, a directional pattern of hybridization was observed from E. albania to other species. Phylogenetic study through DNA sequencing confirmed the existence of three clades corresponding to the three species previously recognized by morphological and molecular studies. This study underlines the importance of assessing hybridization in evolutionary studies, by tracing the lineage separation process that leads to the origin of new species. Our research demonstrates that hybridization processes have a high occurrence in natural populations.

Predator size divergence depends on community context

Body size is a multi-functional trait related to various fitness components, but the relative importance of different selection pressures is seldom resolved. In Carabus japonicus beetles, of which the larvae exclusively prey on earthworms, adult body size is related to the presence/absence of a larger congener and habitat temperature. In sympatry, C. japonicus consistently exhibits smaller body size which is effective for avoiding interspecific mating, but in allopatry, it shows size variation unrelated to temperature. Here, we show that this predator-size variation is attributed to prey-size variation, associated with high phylogenetic diversity in earthworm communities. In allopatry, the predator size was larger where larger prey occurred. Larger adult size may have been selected because larger females produce larger larvae, which can subdue larger prey. Thus, in the absence of a larger congener, variation in prey body size had a pronounced effect on geographic body size divergence in C. japonicus.

Low levels of hybridization in two species of African driver ants.

Hybridization in ants can have consequences different from those observed in most other species, with many of the potential deleterious effects being mitigated due to haplodiploidy and eusociality. In some species where colonies are either headed by multiple queens or single queens that mate with many males, hybridization is associated with genetic caste determination, where hybrids develop into workers and purebred individuals develop into queens. A previous study suggested that hybridization occurs between two Dorylus army ant species with multiply mated queens. However, the extent and exact pattern of hybridization have remained unclear, and its possible effect on caste determination has not been investigated. In this study, we aimed to determine the extent and direction of hybridization by measuring how frequently hybrids occur in colonies of both species, and to investigate the possibility of genetic caste determination. We show that hybridization is bidirectional and occurs at equal rates in both species. Hybrid workers make up only 1-2% of the population, and successful interspecific matings represent approximately 2% of all matings in both species. This shows that, although interspecific matings that give rise to worker offspring occur regularly, they are much rarer than intraspecific mating. Finally, we find no evidence of an association between hybridization and genetic caste determination in this population. This means that genetic caste determination is not a necessary outcome of hybridization in ants, even in species where queens mate with multiple males.

Cladistic classification of Mecyclothorax Sharp (Coleoptera, Carabidae, Moriomorphini) and taxonomic revision of the New Caledonian subgenus Phacothorax Jeannel

The 15 species of Mecyclothorax Sharp precinctive to New Caledonia are revised and shown by cladistic analysis to comprise a monophyletic lineage, here treated as subgenus Phacothorax Jeannel. The New Caledonian species of subgenus Phacothorax include Mecyclothorax fleutiauxi (Jeannel), M. najtae Deuve, and 13 newly described species: M. jeanneli sp. n., M. laterobustus sp. n., M. laterorectus sp. n., M. laterosinuatus sp. n., M. laterovatulus sp. n., M. manautei sp. n., M. megalovatulus sp. n., M. octavius sp. n., M. paniensis sp. n., M. picdupinsensis sp. n., M. plurisetosus sp. n., and two jointly authored species; M. kanak Moore & Liebherr sp. n., and M. mouensis Moore & Liebherr sp. n.. subgenus Phacothorax is one of five subgenera recognized within genus Mecyclothorax based on cladistic analysis of 65 exemplar taxa utilizing information from 137 morphological characters. The four other monophyletic subgenera include the precinctive Australian Eucyclothorax subgen. n. (type species Mecyclothorax blackburni [Sloane]), the precinctive Queensland Qecyclothorax subgen. n. (type species Mecyclothorax storeyi Moore), the precinctive New Zealand Meonochilus Liebherr & Marris status n., and the geographically widespread and very diverse nominate subgenus, distributed from St. Paul and Amsterdam Islands, eastward across Australia and New Guinea, and in the Sundas, Timor Leste, Lord Howe and Norfolk Islands, New Zealand, and the Society and Hawaiian Islands. The biogeographic history of Mecyclothorax can be derived from the parsimony cladogram time-calibrated by times of origin of particular geographic areas inhabited by resident representative species. Based on sister-group status of subgenus Phacothorax and subgenus Mecyclothorax, and occupation of Lord Howe Island–an island originating no earlier than 6 Ma–by the earliest divergent lineage within subgenus Mecyclothorax, the ancestor of present-day Phacothorax spp. is hypothesized to have colonized New Caledonia 6 Ma, subsequent both to Cretaceous Gondwanan vicariance as well as any Oligocene submergence. Area relationships among the New Caledonian Phacothorax point to earliest diversification incorporating the northern massifs, and most recent diversification on the ultramafic volcanic substrates in the south of Grand Terre. Flight wing loss has played an important role in shaping the various island faunas, both in their morphology as well as their diversity. The retention of flight capability in only a few of the many hundred Mecyclothorax spp. is presented in light of how populations evolve from macropterous colonizing propagules to vestigially winged specialists. Interspecific differences in genitalic structures for the sister-species pair M. fleutiauxi + M. jeanneli are shown to involve functional complementarity of male and female structures. Extensive geographic variation of male genitalia is demonstrated for several New Caledonian Mecyclothorax spp. This variation deviates from the geographically uniform male genitalia exhibited by species in the hyperdiverse Mecyclothorax radiation of Haleakalā volcano, Maui, suggesting that extensive sympatry occurring among species in that diverse species swarm selects for stability within this mate recognition system. Conversely, lower levels of sympatry characterizing the depauperate New Caledonian radiation permit the presence of more extensive male genitalic variation, this variation not selected against due to the lower likelihood of interspecific mating mistakes.

Cladistic classification of Mecyclothorax Sharp (Coleoptera, Carabidae, Moriomorphini) and taxonomic revision of the New Caledonian subgenus Phacothorax Jeannel

The 15 species of Mecyclothorax Sharp precinctive to New Caledonia are revised and shown by cladistic analysis to comprise a monophyletic lineage, here treated as subgenus Phacothorax Jeannel. The New Caledonian species of subgenus Phacothorax include Mecyclothoraxfleutiauxi (Jeannel), M.najtae Deuve, and 13 newly described species: M.jeanneli sp. n., M.laterobustus sp. n., M.laterorectus sp. n., M.laterosinuatus sp. n., M.laterovatulus sp. n., M.manautei sp. n., M.megalovatulus sp. n., M.octavius sp. n., M.paniensis sp. n., M.picdupinsensis sp. n., M.plurisetosus sp. n., and two jointly authored species; M.kanak Moore & Liebherr sp. n., and M.mouensis Moore & Liebherr sp. n.. subgenus Phacothorax is one of five subgenera recognized within genus Mecyclothorax based on cladistic analysis of 65 exemplar taxa utilizing information from 137 morphological characters. The four other monophyletic subgenera include the precinctive Australian Eucyclothorax subgen. n. (type species Mecyclothoraxblackburni [Sloane]), the precinctive Queensland Qecyclothorax subgen. n. (type species Mecyclothoraxstoreyi Moore), the precinctive New Zealand Meonochilus Liebherr & Marris status n., and the geographically widespread and very diverse nominate subgenus, distributed from St. Paul and Amsterdam Islands, eastward across Australia and New Guinea, and in the Sundas, Timor Leste, Lord Howe and Norfolk Islands, New Zealand, and the Society and Hawaiian Islands. The biogeographic history of Mecyclothorax can be derived from the parsimony cladogram time-calibrated by times of origin of particular geographic areas inhabited by resident representative species. Based on sister-group status of subgenus Phacothorax and subgenus Mecyclothorax, and occupation of Lord Howe Island–an island originating no earlier than 6 Ma–by the earliest divergent lineage within subgenus Mecyclothorax, the ancestor of present-day Phacothorax spp. is hypothesized to have colonized New Caledonia 6 Ma, subsequent both to Cretaceous Gondwanan vicariance as well as any Oligocene submergence. Area relationships among the New Caledonian Phacothorax point to earliest diversification incorporating the northern massifs, and most recent diversification on the ultramafic volcanic substrates in the south of Grand Terre. Flight wing loss has played an important role in shaping the various island faunas, both in their morphology as well as their diversity. The retention of flight capability in only a few of the many hundred Mecyclothorax spp. is presented in light of how populations evolve from macropterous colonizing propagules to vestigially winged specialists. Interspecific differences in genitalic structures for the sister-species pair M.fleutiauxi + M.jeanneli are shown to involve functional complementarity of male and female structures. Extensive geographic variation of male genitalia is demonstrated for several New Caledonian Mecyclothorax spp. This variation deviates from the geographically uniform male genitalia exhibited by species in the hyperdiverse Mecyclothorax radiation of Haleakalā volcano, Maui, suggesting that extensive sympatry occurring among species in that diverse species swarm selects for stability within this mate recognition system. Conversely, lower levels of sympatry characterizing the depauperate New Caledonian radiation permit the presence of more extensive male genitalic variation, this variation not selected against due to the lower likelihood of interspecific mating mistakes.

Taxonomic revision and insights into the speciation mode of the spider Dysdera erythrina species-complex (Araneae : Dysderidae): sibling species with sympatric distributions

The genus Dysdera Latreille, 1804, a species-rich group of spiders that includes specialised predators of woodlice, contains several complexes of morphologically similar sibling species. Here we investigate species limits in the D. erythrina (Walckenaer, 1802) complex by integrating phenotypic, cytogenetic and molecular data, and use this information to gain further knowledge on its origin and evolution. We describe 16 new species and redescribe four poorly known species belonging to this clade. The distribution of most of the species in the complex is limited to southern France and the north-eastern Iberian Peninsula. The species studied do not show any obvious differences in habitat preference, and some of them even occur sympatrically at certain sites. They probably feed on the same type of prey as they readily capture woodlice. On the other hand, they differ in body size, mouthparts shape, sculpturing of carapace, morphology of the copulatory organs, karyotype and DNA sequences. Experimental interspecific mating showed a partial precopulatory behavioural barrier between D. erythrina and D. cechica, sp. nov. Our data suggest that karyotype evolution of the complex included chromosome fusions and fissions as well as translocations (between autosomes as well as autosomes and sex chromosomes). We hypothesise that chromosome rearrangements generating reproductive incompatibility played a primary role in speciation within Dysdera complexes. Dysdera spiders are poor dispersers, and their original distribution areas (forested areas in the Mediterranean) were repeatedly fragmented during Quarternary climatic oscillations, facilitating integration of chromosome rearrangements into karyotypes by genetic drift. Sympatric occurrence of closely related species may have been promoted by prey segregation as suggested by differentiation in body size in co-occurring species. The following new species are described: D. catalonica, sp. nov., D. cechica, D. dolanskyi, sp. nov., D. fabrorum, sp. nov., D. garrafensis, sp. nov., D. graia, sp. nov., D. kropfi, sp. nov., D. minairo, sp. nov., D. portsensis, sp. nov., D. pradesensis, sp. nov., D. pyrenaica, sp. nov., D. quindecima, sp. nov., D. septima, sp. nov., D. stahlavskyi, sp. nov., D. tredecima, sp. nov. and D. undecima, sp. nov.

Occurrence of Interspecific Mating between Two Species of Danaus Kluk, 1780 (Lepidoptera: Nymphalidae) in Nature

Mating across species occurs rarely in nature, which contends prevalent idea of biological species concept. Throughout species range, mating pattern varies and reproductive barriers are also not fixed among different species. In this study, two instances of interspecific mating between two widely common Nymphalid Tiger butterflies (Danaus Kluk, 1780) in Indian region are reported. Observations imply lack of absolute reproductive barriers, where possible interplay exists among prezygotic and postzygotic isolating factors compensating each other in order to restrain interspecific hybridization.

Interspecific competition, hybridization, and reproductive isolation in secondary contact: missing perspectives on males and females.

Research on sexual selection and hybridization has focused on female mate choice and male–male competition. While the evolutionary outcomes of interspecific female preference have been well explored, we are now gaining a better understanding of the processes by which male–male competition between species in secondary contact promotes reproductive isolation versus hybridization. What is relatively unexplored is the interaction between female choice and male competition, as they can oppose one another or align with similar outcomes for reproductive isolation. The role of female–female competition in hybridization is also not well understood, but could operate similarly to male–male competition in polyandrous and other systems where costs to heterospecific mating are low for females. Reproductive competition between either sex of sympatric species can cause the divergence and/or convergence of sexual signals and recognition, which in turn influences the likelihood for interspecific mating. Future work on species interactions in secondary contact should test the relative influences of both mate choice and competition for mates on hybridization outcomes, and should not ignore the possibilities that females can compete over mating resources, and males can exercise mate choice.

Male origin determines satyrization potential of Aedes aegypti by invasive Aedes albopictus

Rapid displacements of resident Aedes aegypti by invasions of Aedes albopictus have been documented in the southeastern United States and Bermuda. Interspecific mating has been detected in nature between these species and proposed as a likely mechanism for these displacements by means of asymmetric reproductive interference, or satyrization. However, rapid displacements of A. aegypti have not been detected in most localities where these two invasive species are known to co-occur. Aedes albopictus invaded the United States and Brazil at approximately the same time, in the mid-1980s, but the origins of the invading strains are known to be different. Here we tested the hypothesis, in standardized cage environments, that A. albopictus males from Brazil are less capable of satyrizing A. aegypti females than A. albopictus males from the United States. Using strains of A. aegypti and A. albopictus from the United States of known susceptibility to and capacity for interspecific mating, we demonstrate that A. albopictus colonized from collections in the Brazilian cities of Rio de Janeiro and Manaus were relatively unsuccessful in inseminating virgin female A. aegypti from Key West Florida compared to A. albopictus from peninsular Florida. We suggest that the low satyrization potential of Brazilian A. albopictus males may contribute to the lack of documented competitive displacements of A. aegypti in that country.

Reduced incompatibility in the production of second generation hybrids between two Magnolia species revealed by Bayesian gene dispersal modeling.

Hybrid zones are areas where gene flow between related species is currently occurring, so information on the compatibility between related species and their hybrids is essential for predicting the dynamics of such zones generated by introgressive hybridization. In this study, we quantified the compatibility among Magnolia stellata, M. salicifolia, and their hybrids in a hybrid zone using gene dispersal modeling. After determining the genealogical classes of adult trees in the hybrid zone, the paternity of 574 open-pollinated seeds from 37 known maternal trees was analyzed with microsatellite markers. A neighborhood-based Bayesian gene dispersal model developed by us for estimating compatibility was then applied to the paternity data. When M. stellata or M. salicifolia were mothers, interspecific mating to produce F1 hybrids yielded significant incompatibility, but backcrossing with F1 hybrids did not. Furthermore, when F1 hybrids became mothers, no significant incompatibility resulted from backcrossing to parental species or intra-F1 mating to produce F2 hybrids. The estimated proportion of F1 hybrids in the outcrossed seeds (1.7%) in the hybrid zone was much lower than that in the adult trees (14.0%). While it is difficult to obtain F1 hybrids, their low incompatibility makes it easy to produce advanced generation hybrids, once they have been successfully obtained. Although the production of F1 seeds is rare, heterosis and/or weak selection pressure in an empty niche between the parental species' niches may have contributed to the increased proportion of adult F1 hybrids in the hybrid zone.

Sexual conflict and the evolution of genitalia: male damselflies remove more sperm when mating with a heterospecific female

In Calopteryx damselflies, males remove rivals’ sperm stored by the female, thereby reducing sperm competition. This behaviour may create a sexual conflict, because females could lose the sperm stored in the spermatheca, used for long-term storage. Comparative evidence suggested antagonistic coevolution between sexes, which might prompt the evolution of narrow spermathecal ducts, or longer spermathecae, hindering sperm removal. Calopteryx haemorrhoidalis and C. splendens coexist and sometimes hybridize. Therefore, here I predicted that if females coevolve with conspecific males, heterospecific males should have an advantage when interspecific matings occur because females will show less resistance to them than to conspecific males. By hand-pairing females to males of both species, I found that in intraspecific and interspecific matings, sperm was almost completely removed from the bursa (97–100%), but only partially from the spermathecae, with more spermathecal removal in interspecific (63–71%) than intraspecific matings (14–33%). This suggests that heterospecific males are more efficient in sperm removal as predicted by a sexually-antagonistic coevolutionary scenario. Furthermore, in most cases, only the left spermatheca was emptied, suggesting that the evolution of more than one spermatheca might also be a female counter-adaptation to regain control over fertilization.

The chemical basis of mate recognition in two parasitoid wasp species of the genus Nasonia

AbstractTo recognize one's mate is essential for all sexually reproducing animals. In insects, mate recognition is often based on chemical cues such as hydrocarbons which are distributed over the insect's cuticle. In the parasitoid wasp genus Nasonia (Hymenoptera: Pteromalidae), interspecific mating possibly occurs in microsympatry between Nasonia vitripennis Walker and Nasonia giraulti Darling despite post‐zygotic isolation mechanisms preventing hybridization. Males of N. vitripennis are known to equally court con‐ and heterospecific females, which they recognize by means of cuticular hydrocarbons. A recent study surprisingly showed that this might not be the case in N. giraulti, leaving open how males of this species achieve the recognition of mating partners. In this study, we investigated chemical mate recognition in N. giraulti in more detail and compared observed behaviors with behaviors of N. vitripennis by conducting experiments with both species concurrently and under the same experimental conditions. We disentangled the role of female‐derived non‐polar cuticular lipids – i.e., cuticular hydrocarbons – and more polar cuticular lipids in the ability of males to recognize con‐ and heterospecific females. In addition, we tested whether females of the two species discriminate similarly between con‐ and heterospecific males. We demonstrate that, in contrast to N. vitripennis, males of N. giraulti prefer live conspecific females over heterospecific ones. Furthermore, in contrast to N. vitripennis, mate recognition in N. giraulti males is not based on cuticular hydrocarbons, but rather involves other chemical messengers, presumably more polar cuticular lipids. In both species, discrimination against heterospecific males decreases with female age.

Weak premating isolation between two parapatric brocket deer species

Brocket deer Mazama nemorivaga and M. gouazoubira occur at the Amazon basin and southern areas, respectively, in parapatric distribution ranges. Both species can interbreed in captivity, although hybrids have serious fertility problems. Therefore, we expect natural selection to favour behavioural barriers against interspecific mating. We carried out no-choice tests with individuals of both species in captivity, along with white-tailed deer (Odocoileous virginianus) as outgroup. Behaviours were video recorded and analysed by using Generalized Mixed models, with interacting females and males as random subjects. Trials never led to copulation when the white-tailed-deer male was involved. Copulations within brocket deer species were more likely to occur when the individuals belonged to the same species (82.4%) but they also occurred quite frequently in interspecific interactions (35.7%). We identified some courtship behaviours, in males and females, which associated with a higher copulation probability or showed differences in frequency when performed to partners of the same or different species. In conclusion, our results reveal that the occurrence of facilitating behaviours and copulations were more common in intraspecific interactions, evidencing discrimination between species, but also that the precopulatory barrier was not strong between both brocket deer species.

A generalized population dynamics model for reproductive interference with absolute density dependence

Interspecific mating interactions, or reproductive interference, can affect population dynamics, species distribution and abundance. Previous population dynamics models have assumed that the impact of frequency-dependent reproductive interference depends on the relative abundances of species. However, this assumption could be an oversimplification inappropriate for making quantitative predictions. Therefore, a more general model to forecast population dynamics in the presence of reproductive interference is required. Here we developed a population dynamics model to describe the absolute density dependence of reproductive interference, which appears likely when encounter rate between individuals is important. Our model (i) can produce diverse shapes of isoclines depending on parameter values and (ii) predicts weaker reproductive interference when absolute density is low. These novel characteristics can create conditions where coexistence is stable and independent from the initial conditions. We assessed the utility of our model in an empirical study using an experimental pair of seed beetle species, Callosobruchus maculatus and Callosobruchus chinensis. Reproductive interference became stronger with increasing total beetle density even when the frequencies of the two species were kept constant. Our model described the effects of absolute density and showed a better fit to the empirical data than the existing model overall.

Male accessory gland proteins affect differentially female sexual receptivity and remating in closely related Drosophila species

In sexual species, mating success depends on the male’s capacity to find sexual partners and on female receptivity to mating. Mating is under evolutionary constraints to prevent interspecific mating and to maximize the reproductive success of both sexes. In Drosophila melanogaster, female receptivity to mating is mainly controlled by Sex peptide (SP, i.e. Acp70A) produced by the male accessory glands with other proteins (Acps). The transfer of SP during copulation dramatically reduces female receptivity to mating and prevents remating with other males. To date, female postmating responses are well-known in D. melanogaster but have been barely investigated in closely-related species or strains exhibiting different mating systems (monoandrous versus polyandrous). Here, we describe the diversity of mating systems in two strains of D. melanogaster and the three species of the yakuba complex. Remating delay and sexual receptivity were measured in cross-experiments following SP orthologs or Acp injections within females. Interestingly, we discovered strong differences between the two strains of D. melanogaster as well as among the three species of the yakuba complex. These results suggest that reproductive behavior is under the control of complex sexual interactions between the sexes and evolves rapidly, even among closely-related species.