Increasing land use drives changes in plant phylogenetic diversity and prevalence of specialists

Abstract

Increased human land use has resulted in the increased homogenization of biodiversity between sites, yet we lack sufficient indicators to predict which species decline and the consequence of their potential loss on ecosystem services. We used comparative phylogenetic analysis to (1) characterize how increasing conversion of forest and grasslands to grazing pasturelands changes plant diversity and composition; (2) examine how changes in land use relate to declines in functional trait diversity; and (3) specifically investigate how these changes in plant composition affect the prevalence of zygomorphy and the possible consequences that these changes may have on pollinator functional groups. As predicted, we found that the conversion to grazing pasturelands negatively impacted species richness and phylogenetic composition. Clades with significantly more represented taxa in grasslands (GL) were genera with a high representation of agricultural weeds, while the composition was biased towards clades of subalpine herbaceous wildflowers in Mixed Forest (MF). Changes in community composition and structure had strong effects on the prevalence of zygomorphic species likely driven by nitrogen-fixing abilities of certain clades with zygomorphic flowers (e.g., Fabaceae). Land conversion can thus have unexpected impacts on trait distributions relevant for the functioning of the community in other capacities (e.g., cascading effects to other trophic levels (i.e., pollinators). Finally, the combination of traits represented by the current composition of species in GL and MF might enhance the diagnostic value of productivity and ecosystem processes in the most eroded ecosystems.

Climate and habitat influences on bee community structure in Western Canada

“…Previous studies indicate that, within terrestrial Canadian ecozones, pollinator diversity is influenced greatly by habitat characteristics, plant composition and climate (Bingham and Orthner 1998;Sheffield et al 2014;Straka and Starzomski 2015). For instance, prairie sites in Alberta tend to support higher proportions flowering plant species with morphological constraints (e.g., zygomorphy of Fabaceae (Villalobos and Vamosi 2016)) compared to sites in the mixedwood plains ecozone and tall grass savannah in Ontario and Quebec. These descriptive studies are important, but we have yet to uncover the major determinants of broad-scale pollinator distribution differences across the different ecozones of the country.…”