摘要: Behavioral flexibility provides an individual with the ability to adapt its behavior in response to environmental changes. Studies on mammals, birds, and teleosts indicate greater behavioral flexibility in females. Conversely, males appear to exhibit greater behavioral persistence. We, therefore, investigated sex differences in behavioral flexibility in 2 closely related molly species (Poecilia latipinna, P. mexicana) and their more distant relative, the guppy P. reticulata by comparing male and female individuals in a serial, visual reversal learning task. Fish were first trained in color discrimination, which was quickly learned by all females (guppies and mollies) and all molly males alike. Despite continued training over more than 72 sessions, male guppies did not learn the general test procedure and were, therefore, excluded from further testing. Once the reward contingency was reversed serially, molly males of both species performed considerably better by inhibiting their previous response and reached the learning criterion significantly faster than their respective conspecific females. Moreover, Atlantic molly males clearly outperformed all other individuals (males and females) and some of them even reached the level of 1-trial learning. Thus, the apparently universal pattern of higher female behavioral flexibility seems to be inverted in the 2 examined molly species, although the evolutionary account of this pattern remains highly speculative. These findings were complemented by the observed lower neophobia of female sailfin mollies compared with their male conspecifics. This sex difference was not observed in Atlantic mollies that were observed to be significantly less distressed in a novel situation than their consexuals. Hypothetically, sex differences in behavioral flexibility can possibly be explained in terms of the different roles that males and females play in mating competition, mate choice, and reproduction or, more generally, in complex social interactions. Each of these characteristics clearly differed between the closely related mollies and the more distantly related guppies.

摘要: To reproduce, males have to fertilize the female's eggs, sometimes in competition with ejaculates of other males. In species where males display alternative reproductive tactics, whereby territorial males secure mating and non-territorial males have to sneak copulations, the latter might be expected to invest relatively more resources towards sperm quality compared with the territorial males. Sperm cells are especially vulnerable to oxidative stress, which reduces male fertility. Therefore, antioxidant resources are expected to modulate sperm quality, and might be allocated differently between reproductive tactics. To test the link between reproductive tactics, redox profile and sperm quality, we experimentally induced changes in the reproductive tactics of 39 captive males Seba's short-tailed bats Carollia perspicillata. We monitored the blood and ejaculate oxidative balance, and the sperm quality before, 7 days and 21 days after the manipulation of reproductive tactic. Although ejaculates' oxidative damage was negatively related to sperm velocity, males exhibited similar blood and ejaculates redox profiles and similar sperm quality, regardless of their reproductive tactic. Possibly, these results arise as a consequence of some constraints having been lifted during the experiment. Our results also suggest that, in Seba's short-tailed bats, the expression of alternative reproductive tactics is not subjected to strong oxidative constraints. Furthermore, our results could reflect an absence of trade-off between pre- and post-copulatory traits in harem males, as they could be selected to invest both in female attraction and sperm quality, as a consequence of their inability to fully monopolize females.

摘要: The interaction between organisms and their environment is central in functional morphology. Differences in habitat usage may imply divergent morphology of locomotor systems; thus, detecting which morphological traits are conservative across lineages and which ones vary under environmental pressure is important in evolutionary studies. We studied internal and external morphology in 28 species of Neotropical anurans. Our aim was to determine if internal morphology (muscle and tendons) shows lower phylogenetic signal than external morphology. In addition, we wanted to know if morphology varies in relation to the habitat use and if there are different functional groups. We found differences in the degree of phylogenetic signal on the groups of traits. Interestingly, postaxial regions of the forelimb are evolutionarily more labile than the preaxial regions. Phylomorphospace plots show that arboreal (jumpers and graspers) and swimmer frogs cluster based on length of fingers and the lack of sesamoid, also reflected by the use of habitat. These functional clusters are also related to phylogeny. Sesamoid and flexor plate dimensions together with digit tendons showed to be important to discriminate functional groups as well as use of habitat classification. Our results allow us to identify a grasping syndrome in the hand of these frogs, where palmar sesamoid and flexor plate are absent and a third metacarpal with a bony knob are typical. Thus, a lighter skeleton, long fingers and a prensile handmay be key for arboreality.

摘要: Sexual differences in morphology can evolve by sexual selection and/or natural selection. In some species, only males have morphological structures that are used as weapons. Since some weapons may also be used for defensive purposes, males and females may behave differently towards predators. In some species of harvestmen (Arachnida and Opiliones), males have sharp apophyses (spines) on their 4th pair of legs whereas females lack them. Those apophyses are used in male-male fights and in antipredatory behaviors. The harvestmen antipredatory repertory also encompasses passive defenses such as thanatosis (death feigning), retaliation (attack on predators), and chemical defense. Due to the sexual differences on weaponry, we hypothesized that males and females of Mischonyx cuspidatus (Gonyleptidae) rely on different defensive strategies. We experimentally induced males and females to perform 3 defensive behaviors: thanatosis, pinching with legs, and chemical release. We predicted that females would engage more in passive and chemical defenses than males, whereas males would rely more on retaliation than females. As expected, females performed thanatosis more often than males. Likewise, males performed retaliation more often than females. We did not find differences in the rate of chemical defense use between the sexes. This study provides evidence that due to sexual dimorphism, alternative antipredatory behaviors may have been selected in the different sexes in M. cuspidatus.

摘要: We obtained geo-referenced occurrence and climatic data from individual localities for 59 species of terrestrial elapid snakes, used phylogenetic generalized least squares regression to investigate spatial and cladistic patterns of variation in climatic niche breadths, and compared patterns within and across regions and clades to see if they parallel or differ from each other. Specifically, we test (1) whether a species' climatic niche breadth on a given niche axis relates to its position along that axis, and to its climatic niche breadth on another niche axis, and (2) whether variation in niche breadths among species is explained by within-locality variation in climatic conditions or by among-locality variation. We found that: (1) there is an overall global pattern, and patterns in individual regions or clades generally parallel each other and global patterns; (2) species in warmer environments have narrower temperature niche breadths (TNBs); (3) precipitation niche breadth (PNB) and position are positively related; (4) TNB and PNB are not related; and (5) within-locality variation in climatic conditions explains most variation in TNBs, whereas among-locality variation explains most variation in PNBs. Our results are consistent with those reported for lizards of the families Phrynosomatidae and Varanidae, confirm the importance of within-locality niche breadth to species niche breadth, and show a more important role of among-locality niche breadth in affecting species niche breadth in terrestrial elapids than in lizards.