Relationships between butterfly foraging and local and landscape floral coverage

A decline in pollinator populations throughout the world is becoming increasingly evident. Unfortunately, much is still unknown about the habitat requirements of these species. This gap in knowledge is particularly poignant in native butterflies of the South Central U.S., as butterflies play a critical role in native plant reproduction and conservation. At the landscape level, studies have suggested a positive relationship between floral diversity and abundance, and pollinator diversity and abundance.  In this research, we examine two main hypotheses: 1) Butterfly diversity is correlated with floral density and diversity at local scales; and 2) butterfly abundance in an area is correlated with floral diversity and density at local scales.

To evaluate these hypotheses, we established 50m X 50m vegetation and butterfly survey study plots in each of 50 sites located across 10 Central and North Central Texas landscapes (5 sites per landscape).  In each plot, two observers netted butterflies for 15 minutes. A 24-hour pan trapping period immediately followed. The floral community of each plot was surveyed in 30 1m² quadrats on the same day of sampling in order to estimate vegetation coverage, floral diversity, and floral density. Sampling occurred in three rounds in May, June, and July of 2012.

Preliminary linear regression analysis revealed that butterfly species diversity and density positively correlated with floral diversity, but not floral density. The increasing butterfly abundance and diversity in response to increasing floral diversity was evident at both the local and landscape levels. Our results suggest that the presence of butterflies in the South Central U.S. more closely linked to floral resource diversity than to floral density. As in many other ecosystems, plant diversity may provide functional diversity in food resources for pollinators, and may provide a longer time period of food resource availability. In light of our results, we suggest that butterfly restoration practices focus on maintaining high floral diversity across both local and landscape scales.