The seahorse genus Hippocampus (Syngnathidae) exhibits extreme morpho

Seagrass ecosystems worldwide have been declining, leading to a decrease in associated fish populations, especially those with low mobility such as syngnathids (pipefish and seahorses). This two-year pilot study investigated seasonal patterns in density, growth, site fidelity, and population dynamics of Tampa Bay (FL) syngnathid fishes at a site adjacent to two marinas under construction. Using a modified mark-recapture technique, fish were collected periodically from three closely located sites that varied in seagrass species (Thalassia spp., Syringodium spp., and mixed-grass sites) and their distance from open water, but had consistent physical/chemical environmental characteristics. Fish were marked, photographed for body size and gender measurements, and released the same day at the capture site. Of the 5695 individuals surveyed, 49 individuals were recaptured, indicating a large, flexible population. Population density peaks were observed in July of both years, with low densities in late winter and late summer. Spatially, syngnathid densities were highest closest to the mouth of the bay and lowest near the shoreline. Seven species of syngnathid fishes were observed, and species-specific patterns of seagrass use emerged during the study. However, only two species, Syngnathus scovelli and Hippocampus zosterae, were observed at high frequencies. For these two species, body size decreased across the study period, but while S. scovelli's population density decreased, H. zosterae's increased. Across six of the seven species, population size declined over the course of this preliminary study; however, seasonal shifts were impossible to distinguish from potential anthropogenic effects of construction.

Observations of hummingbirds feeding at flowers longer or shorter than their bills seem to contradict the view that bill lengths of hummingbirds evolved in concert with the lengths of their flowers. Recent experiments, however, indicate that a hummingbird's ability to feed at artificial flowers of different lengths depends on the widths of the flowers. We examined if the broad range of flower lengths visited by many hummingbird species can be explained by the widths of the flowers. We predicted that both short‐ and long‐billed hummingbirds would include long, wide flower species in their diets, but that short‐billed hummingbirds would not include long, narrow flower species because nectar in these species might be beyond the reach of their bills. If so, the slope of the regression for flower width versus flower length should be smaller for flower species visited by longer‐billed hummingbirds relative to those visited by shorter‐billed hummingbirds. Analyses of data sets for some North American and Monteverde hummingbirds and their food plants were consistent with this prediction, and bill lengths were significantly correlated with the slopes of the regressions of flower width versus length for seven hummingbird species. Comparisons of observed flower use by some Monteverde hummingbird species to flower assemblages generated at random suggest that these significant regressions were not simply a result of allometric relationships between flower lengths and widths, but in some cases reflected active choice by the birds. The two hummingbird–flower data sets also differed significandy in the scaling of corolla width relative to corolla length. In particular, the Monteverde data set contained a large number of long, narrow flower species, which we suggest is a consequence of a different floral evolutionary history and association with long‐billed hummingbird species. The evolutionary effects of hummingbirds and their flowers upon one another are more complex than has generally been realized, and a consideration of corolla length jointly with other floral characters may improve our understanding of hummingbird‐flower relationships.

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Anchialine pond habitats are frequently associated with biota that can differ dramatically from nearby coastal systems. In this study, we investigated lined seahorses Hippocampus erectus by season, size, and sex across a tidal lake on the island of Eleuthera (The Bahamas). In total, 35 benthic transects of 30−60 m 2 were established around the lake margin and assessed 4 times between 2014 and 2016. Seahorses were mapped along each transect and photographed for morphological analyses. Mean (± SE) landscape-level seahorse density was 0.14 ± 0.013 ind. m −2 (max. 0.66 ind. m −2 ), which was substantially higher than worldwide seahorse mean density. Local seahorse density differed both seasonally and spatially, 40% higher in the wet than dry season, and 48.8% lower in the south than in the north end of the lake. Sex-ratio was significantly male-biased in both the north end of the lake and during the wet months. Male mating effort varied seasonally and spatially, with a significantly higher frequency of gravid males in the dry season and the north end of the lake. Male seahorses were significantly larger than females, with additional morphological traits that indicate broader sexual dimorphism. Compared to other seahorse species, Sweetings Pond animals have a higher population density, smaller size at maturity, and a different shape than other H. erectus, indicating a population that is a discrete management unit. Given the CITES Appendix II listing of all seahorses and their decreasing numbers worldwide, this population represents a valuable biological resource that should be managed uniquely.

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