Abstract Detail

Recent Topics Posters

Balogh, Christopher [1], Barrett, Spencer C. H. [2].

Tristyly and invasion revisited: has the frequency of floral morph absence from populations changed over 21 years in Lythrum salicaria (purple loosestrife)?

Founder events and genetic drift can cause the loss of genetic diversity during biological invasion. However, gene flow between populations can restore missing genetic diversity. In tristylous species such as the invasive plant Lythrum salicaria (Lythraceae), computer simulations of finite populations predict asymmetric loss of floral morphs with populations losing the short-styled morph more often than the remaining two morphs. Metapopulation models also demonstrate that even a low rate of gene flow between populations can restore floral morphs that are absent. Thus, patterns of morph-frequency variation in an invaded region will be determined, in part, by the frequency of colonizing episodes and the extent of gene flow.
The purpose of our study was to estimate morph frequency variation in small (~ 100 individuals) populations of L. salicaria in Ontario and to compare our findings to a previous study in the same region conducted in 1992 involving a sample of 102 populations. We hypothesized that because L. salicaria has become much more abundant in the intervening 21 years, gene flow between populations may have reduced the frequency of populations missing floral morphs relative to the earlier study. We sampled 114 populations ranging in size from 3-1000 (median size = 29.5) in the summer of 2013.  Because the 1992 study included more large populations than our study (median size = 126) we only included populations from that survey with < 130 individuals to make population sizes comparable between the two surveys. This resulted in a comparison of 52 populations from 1992 and 101 populations from 2013.
In the 1992 study, 37% of populations lacked at least one morph whereas in 2013 29% of populations lacked at least one morph. This difference is not significant (G = 0.97, df = 1, P > 0.3). As expected based on genetic drift in finite populations, in both years, larger populations were less likely to lack a morph than smaller populations (1992: G = 5.05, df = 1, P < 0.03; 2013: G = 4.76, df = 1, P < 0.03). As predicted by stochastic theory, populations most commonly lacked the short styled morph in both years (morph absence: 1992: L-morph =1, M-morph = 7, S-morph = 14; 2013: L-morph = 4, M-morph = 14, S-morph = 20). Our data revealed relatively little change in morph-frequency variation as the invasion of L. salicaria in Ontario has matured, indicating that stochastic processes play a ubiquitous role in biological invasions regardless of their age.

1 - University of Toronto, Ecology and Evolutionary Biology, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
2 - University Of Toronto, Department Of Ecology & Evolutionary Biology, 25 WILLCOCKS ST, TORONTO, ON, M5S 3B2, Canada

Keywords:
colonization
founder effect
gene flow
Genetic drift
tristyly.

Presentation Type: Recent Topics Poster
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PRT004
Abstract ID:1780
Candidate for Awards:None