Aquatic Sciences Meeting, Albuquerque 2001

SS45 Temporary Aquatic Ecosystems: Here Today, Gone Tomorrow (Spatial and Temporal Connections)

Date: Wednesday, February 14, 2001, Time: 2:30:00 PM

Location: Cochiti/Taos

Howard, S, , University of Texas at El Paso, El Paso, USA, shlob76@hotmail.com

Bonilla, L, , University of Texas at El Paso, El Paso, USA, mlbonilla@utep.edu

Walsh, E, , University of Texas at El Paso, El Paso, USA, ewalsh@utep.edu

THE TIMING OF SEXUAL REPRODUCTION AND SEX ALLOCATION IN ROTIFER POPULATIONS OCCURRING IN TEMPORARY HABITATS

For cyclical parthenogens, there are many competing hypotheses as to when the switch from asexual to sexual reproduction should occur. In addition, cyclical parthenogens are predicted to equally allocate reproductive effort to male and female offspring. Empirical data testing these models are sparse. We sampled 8 populations of monogonont rotifers quantifying population sizes, proportions of population undergoing asexual versus sexual reproduction (mictic ratio, MR), timing of sexual reproduction, and sex allocation ratios (SAR). Rates of sexual reproduction reach up to 75% in small ponds while in the largest pond levels were much lower (2-14%). Average MR for populations ranged from 0.08 to 0.75. In the majority of ponds, sexual reproduction began early and continued throughout the population cycle. SAR varied from 0.16 to 0.89 among ponds and from 0.16 to 0.56 within ponds during different population cycles. However, when ponds from the same geographic locality are combined, the SAR value approached 0.5. Thus our data support predictions of continuous rather than punctuated models regarding the timing of sex and an even sex allocation ratio.

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Aquatic Sciences Meeting, Albuquerque 2001

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