Abstract Detail

Macroevolution

Schenk, John J. [1], Kontur, Sophie [2], Wilson, Hannah [2], Noble, McKayla [1].

Testing for ecological speciation in North American Paronychia (Caryophyllaceae).

The North America species of Paronychia (Caryophyllaceae) are abundant especially in Florida, where nine species occur. Across their ranges, species tend to be associated with particular sand ridges that were created at different times by varying sea levels concomitant with glacial cycles. The species diversity and biogeographic patterns in Paronychia may be attributed to (1) historical geological processes that generated novel habitats for species to diversify allopatrically, (2) ecological speciation, in which species specialize and diversify across an ecological gradient that is associated with different sandhills and sandridges, and/or (3) competitive exclusion. Here, we test the hypothesis that ecological speciation has driven species diversification in Paronychia. If this hypothesis is supported, we expect to find closely related species partitioning into ecologically diverse habitats. Ecological data that included slope, proportion of grain sizes, soil compaction, percent cover, average nearest neighbor, elevation, and 22 soil chemistry properties were collected for all nine species, two putative species, and one outgroup across 46 populations. Populations were also sampled for molecular variation by generating sequences from two chloroplast (matK and trnL-F) and one nuclear ribosomal (ITS) gene to gain perspective into historical ecological diversification. Ecological data were subjected to principal component analyses. We identified at least three separate introductions into Florida from eastern North America. Strong evidence of hybridization was observed between P. baldwinii and P. americana, which belong to separate Floridian introductions, and the closely related P. patula and P. erecta, which belong to the same introduction. While excluding hybrid populations, we observed much overlap in ecological space, with perhaps P. erecta the most distinct cluster. Phenograms constructed with the first three principle components recovered populations of species with as much or greater variation than what was observed among species. Likewise, a disparity through time plot determined greater subclade disparity among populations, which was greater than expectations based on Brownian motion. Taken together, these results suggest that populations occupy a wide spectrum of ecological space and that species are not diversifying through ecological specialization. Two of the three clades exhibited a pattern consistent with habitat formation as sandridges and sandhills formed following decreased sea level as modern day Florida was formed. The third clade consisted of only P. herniarioides, which occurs in the central ridges and extends northward. The current species diversity might be due in part to allopatric diversification associated with the historical process of habitat formation, followed by range expansion and secondary contact.

1 - Georgia Southern University, Department of Biology, 4324 Old Register Road, Statesboro, GA, 30458, USA
2 - Tulane University, Department of Ecology and Evolutionary Biology, New Orleans, LA, 70118, USA

Keywords:
Sandhill
Sandridge
Ecological speciation
speciation
ecology
Paronychia
Caryophyllaceae.

Presentation Type: Oral Paper
Session: 10, Macroevolution
Location: 202/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 2:45 PM
Number: 10006
Abstract ID:351
Candidate for Awards:None