Hesperapis oraria (Balduina bee) is endemic to northern coastal habitats of the Gulf of Mexico and specialized to floral host Balduina angustifolia (Coastal plain honeycomb head). Due to increased threats from coastal fragmentation along the Gulf of Mexico and the floral host specialization and restricted geographic distribution of H. oraria, further investigation into the habitat requirements of this bee is important. This study quantified the habitat use of H. oraria in association with B. angustifolia distribution at regional and landscape spatial scales using classification tree distribution modeling. Barrier island, coastal mainland, and non-coastal mainland areas were surveyed for H. oraria and B. angustifolia throughout most of their known range in Florida including 4 federal parks and military lands and 6 state parks from Perdido Key Florida eastward to St. Joseph peninsula.
Results/Conclusions
Hesperapsis oraria density was lower on barrier island sites compared with coastal mainland sites and H. oraria was not found on non-coastal mainland sites. The number of B. angustifolia patches within an area drove the regional distribution of H. oraria based on thirty predictor variables. At the landscape scale H. oraria presence was predicted most strongly by B. angustifolia patch area, patch density, and patch distance from densely vegetated ephemeral wetlands (swales). The regional distribution of B. angustifolia was based on twenty-three predictor variables and most strongly influenced by the proximity to a bay or the Gulf of Mexico. The optimal classification tree predicted B. angustifolia was present when the patch was greater than 25 meters from a bay or the Gulf of Mexico. Landscape scale distribution of Balduina angustifolia was strongly influenced by the stability of the landscape features in which it was found. The chosen classification tree predicted a B. angustifolia patch would not be found situated within an herbaceous interdunal area, swale, or a washover sand flat. H. oraria conservation strategies should consider maintaining areas with at least 12 patches of B. angustifolia with each patch a minimum of 112 m2, with at minimum B. angustifolia density of 3 plants per m2 and patches found at least 10 m from any ephemeral wetland.