Kay Hodgins
Post-Doctoral Fellow
hodgins(at)zoology.ubc.ca

Ph.D. 2001-2007, University of Toronto
Thesis: The evolution of morph ratios in the tristylous plant Narcissus triandrus (Amaryllidacae) (Advisor: Spencer CH Barrett)

BSc Biology & Anthropology 1997-2001, University of Toronto

My research consists of three complementary areas relating to the evolution of plant populations. Specifically I am interested in: 1) the evolution of plant sexual systems; 2) patterns of selection on floral traits; and 3) genetic approaches to controlling invasive species.

Stylar polymorphisms are classic examples of morphological adaptation between flowers and their pollinators. Heterostyly is one such polymorphism, where there are two (distyly) or three (tristyly) style-morphs within populations. In most heterostylous species, reciprocity of sex-organ position coupled with heteromorphic incompatibility results in symmetrical mating and the evolution of isoplethic (equal) style-morph ratios. However, my PhD work demonstrated that alternatives to this symmetry in form and function are possible. Using parentage analysis and variation at microsatellite loci, I demonstrated for the first time in a heterostylous species the existence of asymmetrical mating patterns among the style-morphs. In particular, I found that imperfect sex-organ reciprocity in the wild daffodil Narcissus triandrus results in asymmetrical mating and the evolution of biased style-morph ratios. These features are the consequence of the unusual association between stylar polymorphism and a self-incompatibility system that permits assortative mating in this species. These empirical results agreed with predictions of pollen transfer models and demonstrated that small but functionally significant variation in floral design governs mating patterns among morphs resulting in the evolution of biased morph ratios.

Measuring natural selection on reproductive traits is critical for understanding the evolution of floral diversification. Hermaphroditic sexual systems require measurements of selection through both female and male function, and this is rarely conducted in outcrossing plants due to difficulties of directly estimating variation in male fitness in wild populations. Despite the importance of male fitness in flowering plants, there is a general paucity of studies in this area because of the difficulty involved in measuring male reproductive success. For my PhD I overcame this issue by developing microsatellite markers and applying complex statistical methods to directly estimate male selection gradients in the wild heterostylous daffodil Narcissus triandrus. I found evidence for selection on traits related to floral design through male function but not female function, probably because floral design is of greater significance for male fitness due to its effects on pollen transfer efficiency. In addition, I found a negative correlation between male and female reproductive success. To our knowledge, this represents the first example of a gender-specific trade-off in reproductive success in a natural population of a hermaphroditic plant. Such trade-offs have important implications for theories concerning the evolution of separate sexes.

 Weeds and invasive plants represent a major threat to biodiversity and impose substantial economic damage to the agriculture industry in Canada. In collaboration with Sarah Otto and Loren Rieseberg, I am exploring the use of selfish genetic elements as a strategy to control weeds and invasive plants. Selfish genetic elements increase in frequency despite causing a reduction in fitness to their host. Specifically, using theoretical models I will assess the possibility of using the selfish genetic elements called cytoplasmic male sterility (CMS), which sterilize male reproductive organs, as a means to control invasive species.  Because CMS elements are inherited maternally, if these elements enhance female fitness they will increase in frequency and can result in population extinction through the evolution of purely female populations. However, in natural populations the loss of hermaphrodites from populations is prevented through the evolution of nuclear restorer genes that reinstate male function. Therefore, my goal to determine the conditions under which the spread of CMS is likely to lead to extinction before the evolution of restores can prevent this outcome.

PUBLICATIONS

Hodgins KA, Rieseberg L, and Otto SP Genetic control of invasive plants species using selfish genetic elements. Evolutionary Applications, accepted.

Hodgins KA, and Barrett SCH (2008) Natural selection on floral traits through male and female function in the wild heterostylous daffodil Narcissus triandrus. Evolution, 62, 1751-1763.

Hodgins KA, and Barrett SCH (2008) Geographic variation in floral morphology and style-morph ratios in a sexually polymorphic daffodil. American Journal of Botany,95, 185-195.

Hodgins KA, and Barrett SCH (2008) Asymmetrical mating patterns and the evolution of biased style-morph ratios in a tristylous daffodil. Genetical Research, 90, 3-15.

Hodgins KA, Barrett SCH (2007) Population structure and genetic diversity in tristylous Narcissus triandrus: insights from microsatellite and chloroplast DNA variation. Molecular Ecology,16, 2317-2332.

Hodgins KA, Stehlik I, Wang P, Barrett SCH (2007) The development of eight microsatellite loci in the wild daffodil Narcissus triandrus (Amaryllidaceae). Molecular Ecology Notes. 7, 510-512.

Hodgins KA, Barrett SCH (2006) Female reproductive success and the evolution of mating-type frequencies in tristylous populations. New Phytologist, 171, 569-580.

Hodgins KA, Barrett SCH (2006) Mating patterns and demography in the tristylous daffodil Narcissus triandrus. Heredity, 96, 262-270.

 

BOOK CHAPTERS

Barrett SCH, Hodgins KA (2006) Floral design and the evolution of asymmetrical mating systems. In: Ecology and Evolution of Flowers (eds. Harder LD & Barrett SCH) pp. 239-254. Oxford University Press, Oxford, UK.

 

R code for simulations examining the invasion of a CMS allele in a 50x50 lattice with edge effects