LIFETIME REPRODUCTIVE SUCCESS,SELECTION, AND THE OPPORTUNITY FOR SELECTION IN THE WHITE-TAILED SKIMMER PLATHEMIS LYDIA (ODONATA: LIBELLULIDAE)

We present estimates of lifetime reproductive success in Plathemis lydia, a territorial dragonfly. We partition the opportunity for selection into multiplicative episodes using the techniques of Arnold and Wade (1984a, 1984b) and measure selection on several morphological and behavioral characters. For both sexes, variance in survivorship was the largest contribution to variance in lifetime reproductive success. Covariance effects are also strong for both sexes, suggesting considerable non-independence of episodes. Opportunity for selection calculated on a daily basis did not approximate analogous values determined from lifetime reproductive success. Phenotypic characters for which we investigated selection included body mass, hind wing length, first date of reproduction, and (for males) an index of territorial aggressiveness. We failed to find any significant direct targets of selection in either males or females. However, the combined effects of direct and indirect selection on early reproduction were significant for males, acting primarily through increased survivorship and increased time per day spent at the pond. Similarly, females present earlier in the season had shorter interclutch intervals. Partitioning of selection acting on male hind wing length and on aggressiveness reveals relationships between selective episodes, possibly indicative of phenotypic trade-offs between natural and sexual selection through male-male competition for females. Division of selection into episodes is a useful technique for identifying the source of selection. However, ordering effects can bias results, except when episodes occur in strictly chronological sequence. We present a method for circumventing this difficulty.     

On the effect of a therapy able to modify both the growth rates in a Gompertz stochastic model

A Gompertz-type diffusion process characterized by the presence of exogenous factors in the drift term is considered. Such a process is able to describe the dynamics of populations in which both the intrinsic rates are modified by means of time-dependent terms. In order to quantify the effect of such terms the evaluation of the relative entropy is made. The first passage time problem through suitable boundaries is studied. Moreover, some simulation results are shown in order to capture the dependence of the involved functions on the parameters. Finally, an application to tumor growth is presented and simulation results are shown.     

Plasma metabolite levels predict bird growth rates: A field test of model predictive ability

Bird growth rates are usually derived from nonlinear relationships between age and some morphological structure, but this procedure may be limited by several factors. To date, nothing is known about the capacity of plasma metabolite profiling to predict chick growth rates. Based on laboratory-trials, we here develop predictive logistic models of body mass, and tarsus and wing length growth rates in Gull-billed Tern Gelochelidon nilotica chicks from measurements of plasma metabolite levels at different developmental stages. The predictive model obtained during the fastest growth period (at the age of 12 days) explained 65-68% of the chicks' growth rates, with fasting triglyceride level explaining most of the variation in growth rate. At the end of pre-fledging period, β-hydroxybutyrate level was also a good predictor of growth rates. Finally, we carried out a field test to check the predictive capacity of the models in two colonies of wild Gull-billed Tern, comparing field-measured and model-predicted growth rates between groups. Both, measured and predicted growth rates, matched statistically. Plasma metabolite levels can thus be applied in comparative studies of chick growth rates when semi-precocial birds can be captured only once.     

Evolutionary patterns of two major reproduction candidate genes (Zp2 and Zp3) reveal no contribution to reproductive isolation between bovine species

Background  

It has been established that mammalian egg zona pellucida (ZP) glycoproteins are responsible for species-restricted binding of sperm to unfertilized eggs, inducing the sperm acrosome reaction, and preventing polyspermy. In mammals, ZP apparently represents a barrier to heterospecific fertilization and thus probably contributes to reproductive isolation between species. The evolutionary relationships between some members of the tribe Bovini are complex and highly debatable, particularly, those involving Bos and Bison species for which interspecific hybridization is extensively documented. Because reproductive isolation is known to be a major precursor of species divergence, testing evolutionary patterns of ZP glycoproteins may shed some light into the speciation process of these species. To this end, we have examined intraspecific and interspecific genetic variation of two ZP genes (Zp2 and Zp3) for seven representative species (111 individuals) from the Bovini tribe, including five species from Bos and Bison, and two species each from genera Bubalus and Syncerus.     

Ca(2+)-dependent and independent mitochondrial damage in hepatocellular injury

The alterations of mitochondrial membrane potential during the development of irreversible cell damage were investigated by measuring rhodamine-123 uptake and distribution in primary cultures as well as in suspensions of rat hepatocytes exposed to different toxic agents. Direct and indirect mechanisms of mitochondrial damage have been identified and a role for Ca2+ in the development of this type of injury by selected compounds was assessed by using extracellular as well as intracellular Ca2+ chelators. In addition, mitochondrial uncoupling by carbonylcyanide-m-chloro-phenylhydrazone (CCCP) resulted in a marked depletion of cellular ATP that was followed by an increase in cytosolic Ca2+ concentration, immediately preceding cell death. These results support the existence of a close relationship linking, in a sort of reverberating circuit, the occurrence of mitochondrial dysfunction and the alterations in cellular Ca2+ homeostasis during hepatocyte injury.