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Abstract Detail


Soto, Tatyana [1], Oakley, Christopher [1].

Heterosis and inbreeding depression in two cleistogamous Ruellia species with contrasting mating systems.

There is an abundance of diversity in the degree of selfing and outcrossing in angiosperms, with a third of angiosperms displaying mixed mating. Selfing can result in inbreeding depression, the reduction in fitness due to an accumulation of recessive, deleterious alleles. With repeated selfing, strongly deleterious alleles can be purged from a population, but some mildly deleterious alleles will be fixed by drift. Cleistogamy is an excellent model system to investigate the role that mutational load plays in the maintenance of mixed mating. Dimorphic cleistogamy refers to an individual producing both closed, obligate self-fertilizing cleistogamous flowers (CL), and open, potentially outcrossing chasmogamous flowers (CH). CL flowers are highly reduced in size, energetically inexpensive, and provide reproductive assurance. Cleistogamy has evolved in nearly 700 species with no documented cases of the loss of CH flowers despite the overwhelming benefits of CL flowers. Avoidance of inbreeding depression could provide an advantage of CH flowers, but very few studies directly estimate inbreeding depression by comparing CH-selfed and CH-outcrossed progeny in cleistogamous species. The few direct estimates we have are insufficient to explain the maintenance of CH flowers. Another proposed advantage of CH flowers is heterosis in occasional outcrossing between populations, though heterosis has yet to be quantified in a cleistogamous species. Heterosis is the increase in fitness of progeny from interpopulation crosses compared to those from intrapopulation crosses. This is due to dominance complementation of deleterious recessive alleles. Here I plan to estimate inbreeding depression and heterosis in two cleistogamous species in the genus Ruellia (Acanthaceae). Ruellia humilis Nutt. produces relatively more CH flowers than Ruellia strepens L.. We predict greater inbreeding depression and less heterosis for R. humilis compared to R. strepens because of the potential for more outcrossing via CH flowers. To quantify inbreeding depression and heterosis I am performing three cross types (CH-self, CH-within, CH-between) on replicate maternal lines from three populations of each species. While this is a work in progress, I will measure fitness components of the progeny derived from these crosses, including germination timing/proportion, survival, and total number of flowers per individual. Quantifying both inbreeding depression and heterosis will accomplish two goals. 1) Reveal the extent to which low inbreeding depression within populations is due to fixed deleterious alleles. 2) Evaluate evidence for heterosis acting as the mechanism maintaining costly CH flowers because they are necessary for interpopulation outcrossing.

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1 - Purdue University, Botany And Plant Pathology, 915 W State Street, West Lafayette, IN, 47907, United States

inbreeding depression
mating system

Presentation Type: Poster
Session: P1, Ecology Posters
Location: Virtual/Virtual
Date: Monday, July 19th, 2021
Time: 5:00 PM(EDT)
Number: P1EC009
Abstract ID:421
Candidate for Awards:None

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