Abstract Detail

Biogeography

Kunkel, David [1], Fishbein, Mark [2].

Niche Differentiation Within the "Asperula Clade" of Asclepias (Apocynaceae).

The ecological niche describes the conditions under which a species can persist and can be used to make predictions about the coexistence of species. Assessing niche differences between closely related species is important for understanding how these species diverged, as well as for how they may coexist across a landscape. To examine niche differences among closely related species, I utilized the “asperula clade” which contains 6 species of Asclepias, A. viridis, A. asperula, A. labriformis, A. welshii, A. involucrata, and A. macrosperma. These milkweeds are primarily located in west and southwest North America, with the exception of A. viridis. I hypothesized that these species differentiate along both climatic and edaphic gradients, primarily precipitation and soil texture (sand, silt, clay). Here, I utilized niche components that include 19 bioclimatic variables, elevation, % clay content, % silt content, % sand content, coarse fragments, nitrogen content, pH, and electrical conductivity to characterize the climatic and substrate niches of this clade. I used a combination of analyses including principal component analysis (PCA), linear discriminant function analysis (LDA), and ecological niche modeling to characterize the niches of these six species, as well as determine potential differences in niche characters between them. In the PCA analysis, PC1 accounted for the most variation between species (40.92%) with the western and southwestern species differentiating from A. viridis through a combination of climatic and edaphic characters, such as mean diurnal range, elevation, coarse fragments, and sand. In this analysis, A. asperula appears to be an intermediate between the cluster of western and southwestern species and A. viridis. In the LDA, a similar pattern of differentiation is observed to that of the PCA. The results of the ecological niche models were used to conduct tests of niche overlap that determine the degree to which niche models of two species are identical or not. We find that the highest degree of niche overlap occurs in sister species with a few notable exceptions, A. asperula and A. involucrata, A. labriformis and A. macrosperma, and A. welshii and A. macrosperma.

1 - 208 S Duncan St, Apt 3, Stillwater, OK, 74074, United States
2 - Oklahoma State University, Dept Of Plant Biology, Ecology & Evolution, 301 Physical Science, Stillwater, OK, 74078, United States

Keywords:
Ecological niche model
Climatic niche
Edaphic Niche
Asclepias.

Presentation Type: Oral Paper
Number: BIOG III009
Abstract ID:428
Candidate for Awards:None