Male size mediates plastic response to winner-loser effects for some sexually selected traits

The outcomes of fights often affect the fitness of males by determining their access to mates. ‘Winner-loser’ effects, where winners often win their next contest, but losers tend to lose, can therefore influence how males allocate resources towards traits under pre- and post-copulatory sexual selection. We experimentally manipulated the winning/losing experiences of size-matched male Gambusia holbrooki for either a day, a week or three weeks to test whether prior winning/losing experiences differentially affect the plasticity of male investment into either mating effort (pre-copulatory) or ejaculates (post-copulatory). Winners had better pre-copulatory outcomes than losers for three of the four traits we measured: number of mating attempts, number of successful attempts, and time spent with the female. Winners also produced faster sperm than losers, but there was no difference in total sperm counts. Interestingly, absolute male size, an important predictor of fighting success, mediated the effect of winning or losing on how long males then spent near a female. Smaller winners spent more time with the female than did larger winners, suggesting that how males respond to prior social experiences is size-dependent. We discuss the general importance of controlling for inherent male condition when comparing male investment into condition-dependent traits.

A GIS Modeling Study of the Distribution of Viviparous Invasive Alien Fish Species in Eastern Europe in Terms of Global Climate Change, as Exemplified by Poecilia reticulata Peters, 1859 and Gambusia holbrooki Girarg, 1859

The potential distribution of tropical fish species in Eastern Europe—Gambusia holbrooki (introduced for biological control) and Poecilia reticulata (aquarium species, found in waste waters of big cities)—tend to be of particular interest in terms of global climate change. After GIS modeling of our own data and findings listed in the GBIF databases (2278 points for G. holbrooki and 1410 points for P. reticulata) using the Maxent package and ‘ntbox’ package in R, 18 uncorrelated variables of 35 Bioclim climatic parameters from CliMond dataset, it was found out that by 2090 guppies will appear in the south of Ukraine (Danube river’s estuary, as well as in several places in the Caucasus and Turkey with habitat suitability > 0.3–0.5). G. holbrooki will also slightly expand its range in Europe. Limiting factors for G. holbrooki distribution are: bio1 (Annual mean temperature, optimum +12–+24 °C) and bio19 (Precipitation of coldest quarter (mm). Limiting factors for P. reticulata are: bio1 (optimum +14–+28 °C), bio4 (Temperature seasonality), bio3 (Isothermality). Unlike G. holbrooki, guppies prefer warmer waters. Such thermophilic fish species do not compete with the native ichthyofauna, but they can occupy niches in anthropogenically transformed habitats, playing an important role as agents of biological control.