Male mating behaviour of a molly, <Emphasis Type="Italic">Poecilia latipunctata</Emphasis>: a third host for the sperm-dependent Amazon molly, <Emphasis Type="Italic">Poecilia formosa</Emphasis>

The Tamesí molly, Poecilia latipunctata, has a very limited biogeographical range in northeast Mexico. This area is nested within the ranges of the Atlantic molly, Poecilia mexicana, and the unisexual Amazon molly, Poecilia formosa. Based on morphology, especially fin shape, the Tamesí molly has been considered to be a "short-fin" molly. We describe the courtship sequence of P. latipunctata. The courtship clearly places the species into the clade of "long-fin" mollies, a finding that corroborates earlier studies based on nuclear DNA and mitochondrial DNA. All three species live together in certain habitats. This renders P. latipunctata a potential host species for the sperm-dependent, unisexual Amazon molly. Using behavioural tests, we demonstrate that P. latipunctata males actually copulate with Amazon mollies, despite a pronounced preference for conspecific females. In laboratory experiments P. latipunctata males are capable of triggering embryogenesis in P. formosa females. Field observations support the hypothesis that P. latipunctata is a third host species for P. formosa, indicating that the Amazon molly effectively exploits all available host species for its gynogenetic mode of reproduction. Electronic Publication     

Female preference for large males in sailfin mollies,<Emphasis Type="Italic"> Poecilia latipinna</Emphasis>: the importance of predation pressure and reproductive status

We examined the effect of predation risk on female association patterns in the live-bearing sailfin molly (Poecilia latipinna). We tested two classes of females, with and without the risk of predation by a green sunfish (Lepomis cyanellus): (1) postpartum females (maintained with males until visibly gravid, then isolated and tested within 24–48 h of dropping a brood); and (2) non-postpartum females (different females, isolated from males for >50 days). When there was no apparent risk of predation, postpartum females showed a significant preference for large over small males, whereas non-postpartum females showed no size preference at all. When there was an apparent risk of predation, postpartum females maintained their preference for larger males and non-postpartum females continued to show no preference for large or small males. These results suggest that reproductive status (receptivity) plays a greater role in mate preference than predation risk. For postpartum females, the cost of not choosing a preferred mate may outweigh the potential cost of predation. Non-postpartum females either do not benefit from mating or are being indecisive about mating and thus are less likely to be choosy whether or not a predator is present.Communicated by I. Schlupp     

Nonlinkage of major histocompatibility complex class I and class II loci in bony fishes

 In tetrapods, the functional (classical) class I and class II B loci of the major histocompatibility complex (Mhc) are tightly linked in a single chromosomal region. In an earlier study, we demonstrated that in the zebrafish, Danio rerio, order Cypriniformes, the two classes are present on different chromosomes. Here, we show that the situation is similar in the stickleback, Gasterosteus aculeatus, order Gasterosteiformes, the common guppy, Poecilia reticulata, order Cyprinodontiformes, and the cichlid fish Oreochromis niloticus, order Perciformes. These data, together with unpublished results from other laboratories suggest that in all Euteleostei, the classical class I and class II B loci are in separate linkage groups, and that in at least some of these taxa, the class II loci are in two different groups. Since Euteleostei are at least as numerous as tetrapods, in approximately one-half of jawed vertebrates, the class I and class II regions are not linked. Received: 30 August 1999 / Revised: 20 October 1999     

How might Gyrodactylus parasitism modify trade-offs between female preference and susceptibility of males to predation in Trinidadian guppies?

A number of examples exist of trade-offs between mating success and survival; that is, success in one fitness component comes at the cost of success in the other fitness component. However, these expected trade-offs are – perhaps even more commonly – not observed. One explanation for this apparent paradox of missing trade-offs could be that the other factors generating fitness variation across individuals confound or obscure the expected trade-off. These confounding effects could arise in two general ways: (i) the additional source of variation could positively (or negatively) influence both fitness components (“shared confounder” hypothesis), or (ii) the additional source of variation could influence only one fitness component (“non-shared confounder” hypothesis). We tested whether parasitism by Gyrodactylus spp. could be a confounder of trade-offs between female preference and susceptibility to predation for male Trinidadian guppies (Poecilia reticulata). As in previous work, we did not find the expected trade-off; that is, the males preferred by females were not more likely to be eaten by predators. Because half of the experimental males were infected by Gyrodactylus in a paired design, we were able to show that females discriminated against infected males, but that infected males were not more susceptible to predation. Our results thus provide support for the non-shared confounder hypothesis. That is, by negatively affecting one fitness component (female choice) but not the other (susceptibility to predation), parasitism by Gyrodactylus could obscure the expected trade-off between female preference and susceptibility to predation.     

Studies on the antileishmanial properties of the antimicrobial peptides temporin A,B and 1Sa

Given the paucity and toxicity of available drugs for leishmaniasis, coupled with the advent of drug resistance, the discovery of new therapies for this neglected tropical disease is recognised as being of the utmost urgency. As such antimicrobial peptides (AMPs) have been proposed as promising compounds against the causative Leishmania species, insect vector‐borne protozoan parasites. Here the AMP temporins A, B and 1Sa have been synthesised and screened for activity against Leishmania mexicana insect stage promastigotes and mammalian stage amastigotes, a significant cause of human cutaneous disease. In contrast to previous studies with other species the activity of these AMPs against L. mexicana amastigotes was low. This suggests that amastigotes from different Leishmania species display varying susceptibility to peptides from the temporin family, perhaps indicating differences in their surface structure, the proposed target of these AMPs. In contrast, insect stage L. mexicana promastigotes were sensitive to two of the screened temporins which clearly demonstrates the importance of screening AMPs against both forms of the parasite. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.     

An indigenous religious ritual selects for resistance to a toxicant in a livebearing fish

Human-induced environmental change can affect the evolutionary trajectory of populations. In Mexico, indigenous Zoque people annually introduce barbasco, a fish toxicant, into the Cueva del Azufre to harvest fish during a religious ceremony. Here, we investigated tolerance to barbasco in fish from sites exposed and unexposed to the ritual. We found that barbasco tolerance increases with body size and differs between the sexes. Furthermore, fish from sites exposed to the ceremony had a significantly higher tolerance. Consequently, the annual ceremony may not only affect population structure and gene flow among habitat types, but the increased tolerance in exposed fish may indicate adaptation to human cultural practices in a natural population on a very small spatial scale.     

Intrinsic reproductive isolation between Trinidadian populations of the guppy, Poecilia reticulata

Although Trinidadian populations of the guppy, Poecilia reticulata, show considerable adaptive genetic differentiation, they have been assumed to show little or no reproductive isolation. We tested this assumption by crossing Caroni (Tacarigua River) and Oropuche (Oropuche R.) drainage populations from Trinidad's Northern Range, and by examining multiple aspects of reproductive compatibility in the F1, F2 and BC1 generations. In open-aquarium experiments, F1 males performed fewer numbers of mating behaviours relative to parental population controls. This is the first documentation of hybrid behavioural sterility within a species, and it suggests that such sterility may feasibly be involved in causing speciation. The crosses also uncovered hybrid breakdown for embryo viability, brood size and sperm counts. In contrast, no reductions in female fertility were detected, indicating that guppies obey Haldane's rule for sterility. Intrinsic isolation currently presents a much stronger obstacle to gene flow than behavioural isolation, and our results indicate that Trinidadian populations constitute a useful model for investigating incipient speciation.     

Behavioral correlations across breeding contexts provide a mechanism for a cost of aggression

Identifying correlations among behaviors is important for understandinghow selection shapes the phenotype. Correlated behaviors canindicate constraints on the evolution of behavioral plasticityor may reflect selection for functional integration among behaviors.Obligate cavity-nesting birds provide an opportunity to examinethese correlations because males must defend limited nest cavitieswhile also competing for mating opportunities and providingparental care. Here, I investigated the role of behavioral correlationsin producing a counterintuitive relationship between nest defenseand reproductive success in western bluebirds (Sialia mexicana)such that males that defended their nests most intensely hadthe lowest reproductive success, measured as the number of withinand extrapair offspring that fledged. By experimentally measuringaggression across contexts, I show that this cost of nest defensewas due to the correlated expression of aggression across thecontexts of nest defense and male–male competition coupledwith a trade-off between male–male aggression and parentalcare. In particular, more aggressive males provisioned theirfemales less during incubation and this led to disrupted incubationpatterns and fewer fledged offspring. However, aggressive malesdid not benefit from avoiding parental investment by gainingextrapair fertilizations, and thus, it is unclear how high levelsof aggression are maintained in this population despite apparentcosts. These results suggest that there are constraints to theevolution of plasticity in aggression and emphasize the importanceof considering the integrated behavioral phenotype to understandhow variation in behavior is linked to fitness.