| The ability of organisms to positively respond to shifts in past climates has been historically crucial for their survival. Similarly, it is essential that organisms adapt to the rapidly changing contemporary climate. Precipitation patterns are predicted to shift, and some areas that were wet in the past, will become dry. The study investigated the influence of precipitation on reproductive biology, trophic ecology, and ecomorphology by contrasting eight species of euryhaline fishes, Poecilia, across wet Central America and dry northern South America.;A time-calibrated phylogeny was constructed, and revealed that South America was invaded multiple times by Poecilia. Female-standard length was related to female-reproductive traits. The large-wet-regime females had larger offspring, while the small-dry-regime females were more fecund. Dry-regime species exhibited larger and more variable core niches, compared to the wet-regime species. Using whole-body, head, and jaw morphologies, species clustered according to precipitation regime, which suggested that physiological responses differed in accordance with environmental regimes. Feeding-ecology traits were significantly correlated with morphology, and showed an association between short guts, C4 habitats, and high-trophic levels with dry-regime species. Scaling of variances of life-history traits showed that most ecological traits structured mid to low in spatial scale, suggesting that the differences in traits were evenly distributed across the region, and allowed for many slightly-differing subpopulations.;Most life-history traits of the wet-regime populations were highly variable (except trophic niches), and overlapped the traits of the dry-regime populations. Although, trophic-niche variability in the wet regime was low, there was overlap in core-niches across precipitation regimes, high variability in ecomorphology, and potential for unobserved wet-regime-trophic niches. This suggests that the variability that was present may be sufficient for the wet-regime species to trophically transition to xeric environments. Therefore, in scenarios of future shifts in precipitation regimes, it appears that the wet-regime species may be primed for adaptation, as they already possessed many of the traits conducive to survival under dry conditions. Especially since wet-regime reproductive and ecomorphological traits had large variances that would be amendable, and would respond well, to varying external pressures, then given adequate time these species will adjust to those changing conditions. |
