Phenotypic variation in a neotropical understory bird driven by environmental change in an urbanizing Amazonian landscape

Environmental change through habitat fragmentation and urbanization drives biodiversity loss in the Neotropics at an alarming rate. Some individuals and species confined to habitat fragments may develop phenotypic adjustments that allow populations to persist, even in landscapes made harsh by human activities. Behavioral and morphological adjustments may enhance a population's ability to cope with anthropogenic hazards. We examined potential differences in the behavioral and morphological phenotype of populations of the neotropical Wedge-billed Woodcreeper (Glyphorynchus spirurus)-an understory forest specialist insectivorous bird-between populations from urban fragmented forests and continuous preserved forests. We evaluated exploratory behavior and morphological traits using generalized linear models and linear discriminant analysis to quantify phenotypical differences among populations. We used failure time analysis to compare latency to explore and move during exploration in a Novel Environment Test (NET). Our analyses detected differences in certain movement behaviors (latencies to move during NET), indicating that individuals from fragmented forests are slow explorers in relation to individuals from the continuous forest. We also found shorter tarsi and tails in the fragmented forest population which were attributed to an overall reduction in body size in these populations. Our results suggest that environmental change driven by fragmentation in an urban landscape is causing population differentiation, but we cannot ascribe observed variations to evolutionary processes only, as the differences observed may be explained by other processes too. However, we suggest that phenotypic differences may be aiding this small understory forest specialist to persist in an urban fragmented landscape.

Evaluating the potential for prezygotic isolation and hybridization between landlocked and anadromous alewife (Alosa pseudoharengus) following secondary contact

The recent increase in river restoration projects is altering habitat connectivity for many aquatic species, increasing the chance that previously isolated populations will come into secondary contact. Anadromous and landlocked alewife (Alosa pseudoharengus) are currently undergoing secondary contact as a result of a fishway installation at Rogers Lake in Old Lyme, Connecticut. To determine the degree of prezygotic isolation and potential for hybridization between alewife life history forms, we constructed spawning time distributions for two anadromous and three landlocked alewife populations using otolith-derived age estimates. In addition, we analyzed long-term data from anadromous alewife migratory spawning runs to look for trends in arrival date and spawning time. Our results indicated that anadromous alewife spawned earlier and over a shorter duration than landlocked alewife, but 3%-13% of landlocked alewife spawning overlapped with the anadromous alewife spawning period. The degree of spawning time overlap was primarily driven by annual and population-level variation in the timing of spawning by landlocked alewife, whereas the timing and duration of spawning for anadromous alewife were found to be relatively invariant among years in our study system. For alewife and many other anadromous fish species, the increase in fish passage river restoration projects in the coming decades will re-establish habitat connectivity and may bring isolated populations into contact. Hybridization between life history forms may occur when prezygotic isolating mechanisms are minimal, leading to potentially rapid ecological and evolutionary changes in restored habitats.