Having sex, yes, but with whom? Inferences from fungi on the evolution of anisogamy and mating types. Biol Rev Camb Philos Soc

Université Lille Nord de France, USTL, GEPV, CNRS, FRE 3268, Villeneuve d'Ascq, France.
Biological Reviews (Impact Factor: 9.67). 05/2011; 86(2):421-42. DOI: 10.1111/j.1469-185X.2010.00153.x
Source: PubMed


The advantage of sex has been among the most debated issues in biology. Surprisingly, the question of why sexual reproduction generally requires the combination of distinct gamete classes, such as small and large gametes, or gametes with different mating types, has been much less investigated. Why do systems with alternative gamete classes (i.e. systems with either anisogamy or mating types or both) appear even though they restrict the probability of finding a compatible mating partner? Why does the number of gamete classes vary from zero to thousands, with most often only two classes? We review here the hypotheses proposed to explain the origin, maintenance, number, and loss of gamete classes. We argue that fungi represent highly suitable models to help resolve issues related to the evolution of distinct gamete classes, because the number of mating types vary from zero to thousands across taxa, anisogamy is present or not, and because there are frequent transitions between these conditions. We review the nature and number of gamete classes in fungi, and we attempt to draw inferences from these data on the evolutionary forces responsible for their appearance, loss or maintenance, and number.

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    • "The two alleles have been described as idiomorphs due to the complete lack of sequence identity, and are commonly referred to as MAT1-1 and MAT1-2 (Turgeon et al., 1993; Turgeon and Yoder, 2000). Homothallic species usually possess both idiomorphs in tandem in the same nucleus (Yun et al., 1999), but other mechanisms exist that can lead to a homothallic phenotype (reviewed in Billiard et al., 2011). The genus Colletotrichum is an exception, with all species studied to date having unusual mating systems that do not conform to these two categories. "
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    • "This division works regardless of primary or secondary traits. For a recent review about why in most species there are only two sexes and why fungi are an exception can help to understand the origins of binary sex, see Billiard et al. (2011). Gender matters but we cannot agree with the simplified definition of gender which is ''how some groups make distinctions ,''equaling gender to femininity and masculinity (p. "

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