Christopher Balogh, Ph.D. student

Department of Ecology and Evolutionary Biology
University of Toronto
25 Willcocks Street
Toronto, Ontario, Canada
M5S 3B2

Office: Earth Science Building 2043, , 416-978-8324
Email: chris.balogh@mail.utoronto.ca

 Degrees

  B. Sc. Biology, Penn State University

 Current Position

  Ph.D. student Department of Ecology and Evolutionary Biology, University of Toronto
Thesis Title: Mating system and pollen dispersal in small populations of an invasive species

  RESEARCH INTETRESTS


Individuals in small populations may lack compatible mates due to a deficit of conspecifics and the stochastic loss of mating types. Both of these factors can favor partial self-compatibility and the invasion of missing mating types into populations. I am currently investigating two questions related to small populations:

  1. Do individuals with higher levels of self-compatibility form colonies more successfully than individuals with lower levels of self-compatibility;
  2. To what degree does gene flow by pollen restore lost mating types to small populations?

 

  Study system

I am studying Lythrum salicaria, a perennial herb introduced from Europe to North America over the past 150 years (Fig 1).

Lythrum

Fig. 1. Inflorescences of Lythrum salicaria (purple loosestrife) at the Koffler Scientific Reserve (KSR) in Ontario.

 

Lythrum salicaria is tristylous with three floral morphs (the long, mid and short-styled morphs; hereafter L-, M-, and S-morphs; Fig. 2). ). In Ontario, ~25% of populations smaller than 500 individuals lack the S-morph. This observation has led to the hypothesis that stochastic forces, such as genetic drift or founder effect, may be responsible for dimorphic populations (Eckert et al. 1996). Important questions remain unanswered concerning the mating system and fertility of small populations and the possibility of the establishment of tristylous populations through gene flow.

 

 

tristyly

Fig. 2. (a) The floral polymorphism tristyly; (b) genotypes for each floral morph at the two diallelic style-length loci (S, M)

 

Reproductive assurance in Lythrum salicaria

Reproductive assurance is frequently invoked to explain the colonization success of invasive plant populations but without much experimental evidence. Although the floral morphs of L. salicaria possess intramorph incompatibility, the M-morph possesses a higher level of partial self-fertility than L- or S-morphs (Darwin 1877; Colautti et al. 2010). Selfing of the M-morph can give rise to L- and M-morph progeny if maternal parents are of genotype ssMm, which is the predominant M-morph genotype in populations at equilibrium (Heuch and Lie 1985). Because almost all dimorphic populations that have been observed lack the S-morph, founder events involving this genotype may give rise to at least some of these dimorphic populations. I am investigating whether partial self-fertility in the M-morph functions to increase the colonization success of the M-morph relative to other style morphs. This will hopefully reveal the role of partial self-fertility in founder events and also demonstrate genetic polymorphism in colonizing potential.

In addition to founding colonies, partial self-fertility may increase the success of individuals in populations without compatible mates. Variability exists in the level of partial self-fertility expressed by the M-morph (Colautti et al. 2010). The reproductive assurance hypothesis predicts that more recently and sparsely colonized areas should possess individuals expressing a higher degree of partial self-fertility (Lloyd 1980). However, this expected trend in the expression of partial self-fertility has not been observed in invasive L. salicaria in Ontario. I am investigating the evolutionary consequences of partial self-fertility by measuring both the variation and genetic basis of this condition and also the fitness of selfed offspring. Through this work I hope to provide new insights into the evolution of partial self-compatibility and its role in the establishment and spread of invasive populations.

Restoration of mating types

Frequency-dependent selection will favor the invasion of missing mating types into dimorphic populations of L. salicaria, thus helping to maintain trimorphism. In contrast to data on morph structure from Ontario, surveys of morph frequency in French and Finnish populations of L. salicaria have shown that they are largely trimorphic (Fig. 3) (Halkka and Halkka 1974; Eckert et al. 1996). Gene flow among populations has been hypothesized to account for these patterns in the native range. However, gene flow has not been examined experimentally in L. salicaria. I plan to investigate the role that pollen dispersal might play in restoring lost morphs to small populations. The goal of this research is to better understand how pollen movement and selection for disassortative mating may reintroduce lost mating types to colonies.

 

Lythrum morph frequencies

Fig. 3. Style-morph frequencies of Lythrum salicaria in populations from France and Ontario. Each large triangle contains points that represent trimorphic (small triangles), dimorphic (squares), or monomorphic (circles) populations. Increasing distance from a side of the triangle represents increasing prevalence of that morph. Populations at the 1:1:1 equilibrium are located in the center of the large triangle.

 References


Colautti, R. I., N. A. White and S. C. H. Barrett. 2010. Variation of self-incompatibility within invasive populations of purple loosestrife (Lythrum salicaria L.) from eastern North America. International Journal of Plant Sciences 171:158–166.

Darwin, C. 1877. The different forms of flowers on plants of the same species. J. Murray, London.

Eckert, C. G., D. Manicacci and S. C. H. Barrett. 1996. Genetic drift and founder effect in native verses introduced populations of an invading plant, Lythrum salicaria (Lythraceae). Evolution 50:1512–1519.

Halkka, O. and L. Halkka. 1974. Polymorphic balance in small island populations of Lythrum salicaria. Annales Botanici Fennici 11:267–270.

Heuch, I. and R. T. Lie. 1985. Genotype frequencies associated with incompatibility systems in tristylous plants. Theoretical Population Biology 27:318–336.

 

 Publications


Balogh CM and Barrett SCH Stochastic processes during invasion: the influence of population size on style-morph frequency variation in Lythrum salicaria (purple loosestrife). International Journal of Plant Sciences: 177

Kariyat, R.R., Mauck, K.E., Balogh, C.M., Stephenson, A.G., Mescher, M.C. & De Moraes, C.M. (2013) Inbreeding in horsenettle (Solanum carolinense) alters night-time volatile emissions that guide oviposition by Manduca sexta moths. Proc. R. Soc. B 2013 280, 20130020, published 27 February 2013. doi: 10.1098/rspb.2013.0020

Kariyat, R.R., Balogh, C.M., Moraski, R.P., De Moraes, C.M., Mescher, M.C. and Stephenson, A.G. (2013) Constitutive and herbivore-induced structural defenses are compromised by inbreeding in Solanum carolinense (Solanaceae)1 American J of Botany (online before print) doi: 10.3732/ajb.120061