# Is Cloning Always Beneficial? The Effects of Asexual Reproduction by Planktonic Feeding Larvae of Sea Stars

## Submission Type

Event

## Faculty Advisor

William Jaeckle

## Expected Graduation Date

2019

## Location

Center for Natural Sciences, Illinois Wesleyan University

## Start Date

4-21-2018 9:00 AM

## End Date

4-21-2018 10:00 AM

## Disciplines

Education

## Abstract

The adaptive value of asexual reproduction by feeding larvae of sea stars is proposed to be an increase in the number of offspring without producing more eggs. However, larval cloning is achieved through loss of tissue and these events may represent a cost to the "parent" larva. We are developing a mathematical model of how female fecundity, mortality rates of larvae, timing of clone production, and estimates of the costs of cloning influence the number of larvae that survive to day 25. Each iteration of the model began with 100,000 zygotes and was replicated for 400 generations. The equation N_{t} = N_{t-1 }× e^{(-m×t)} is the basis for the model, where N_{t} is the number of larvae at time = t (days), N_{t-1 }represents the number of larvae present on the previous day, and m = mortality coefficient for all sources of larval loss. Two models were created to examine these processes. Model R assigns mortality values at random for each day of larval life and Model T allows the mortality rate to decrease linearly with increasing larval size (and age). The mortality values ranged from 0.01 to 0.5 in steps of 0.01. The models explore asexual events in series and in parallel. For 10% - 100% of the parent population cloning on day 7, 14 and 21 of their life span, the number of living clonal larvae that survived to metamorphic competence ranged from 17 - 172, 4 - 37, and 1 - 8 respectively in Model R. In Model T, when 10% - 100% of the parent population reproduce on day 7, 14, and 21 of their life span, the number of living clonal larvae that survived to metamorphic competence ranged from 0 - 5, 0, and 0 respectively. In order for 1 larva to survive to day 25, or to day 50 without cloning must be 60,000, 75,000 or 3,000, 43,000, in Model R and Model T respectively. Hence, any larva generated from a clonal larvae of the original parent generation will not survive to metamorphic competence. Thus, there are cases where the costs of asexual reproduction in sea stars outweigh the benefits.

Is Cloning Always Beneficial? The Effects of Asexual Reproduction by Planktonic Feeding Larvae of Sea Stars

Center for Natural Sciences, Illinois Wesleyan University

The adaptive value of asexual reproduction by feeding larvae of sea stars is proposed to be an increase in the number of offspring without producing more eggs. However, larval cloning is achieved through loss of tissue and these events may represent a cost to the "parent" larva. We are developing a mathematical model of how female fecundity, mortality rates of larvae, timing of clone production, and estimates of the costs of cloning influence the number of larvae that survive to day 25. Each iteration of the model began with 100,000 zygotes and was replicated for 400 generations. The equation N_{t} = N_{t-1 }× e^{(-m×t)} is the basis for the model, where N_{t} is the number of larvae at time = t (days), N_{t-1 }represents the number of larvae present on the previous day, and m = mortality coefficient for all sources of larval loss. Two models were created to examine these processes. Model R assigns mortality values at random for each day of larval life and Model T allows the mortality rate to decrease linearly with increasing larval size (and age). The mortality values ranged from 0.01 to 0.5 in steps of 0.01. The models explore asexual events in series and in parallel. For 10% - 100% of the parent population cloning on day 7, 14 and 21 of their life span, the number of living clonal larvae that survived to metamorphic competence ranged from 17 - 172, 4 - 37, and 1 - 8 respectively in Model R. In Model T, when 10% - 100% of the parent population reproduce on day 7, 14, and 21 of their life span, the number of living clonal larvae that survived to metamorphic competence ranged from 0 - 5, 0, and 0 respectively. In order for 1 larva to survive to day 25, or to day 50 without cloning must be 60,000, 75,000 or 3,000, 43,000, in Model R and Model T respectively. Hence, any larva generated from a clonal larvae of the original parent generation will not survive to metamorphic competence. Thus, there are cases where the costs of asexual reproduction in sea stars outweigh the benefits.