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.
Highlights
Natural communities are currently facing extensive land use modifications, which have the potential to greatly alter species composition and structure (Smart et al, 2006; Watts et al, 2012)
We explore whether: (1) increasing land use is correlated with changes in plant species diversity and composition; (2) changes in land use relate to declines in phylogenetic diversity and community structure; and (3) declines in phylogenetic diversity relate to declines in diversity of a trait, such as zygomorphy, that potentially offers an indicator towards predicting the vulnerability of plant assemblages
We compiled a database of flowering plant communities using The Alberta Biodiversity Monitoring Institute (ABMI) vascular plant lists
Summary
Natural communities are currently facing extensive land use modifications, which have the potential to greatly alter species composition and structure (Smart et al, 2006; Watts et al, 2012). The traits that determine whether a species can persist in a given habitat are likely those that allow survival under changing environmental conditions (Mouillot et al, 2013), yet this may have consequences on the prevalence of other traits that may affect ecosystem functioning. Grasslands in particular have recently been noted as especially susceptible to land use changes (Weiner et al, 2011), with the effects on plant species composition having consequences to plant–pollinator mutualisms (Clough et al, 2014). Emerging studies indicate the loss of more specialised species due to their highly vulnerability to habitat loss (Weiner et al, 2011; Dulvy et al, 2014)
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