Monday, January 17, 2011

Sex is the mechanism of speciation! - For the Septicks

Some people truly become annoyed with the following What Ifs:
  1. What if speciation is more than an handy classification?
  2. What if speciation is an acquired skill?
  3. What if Sexual Selection is the mechanism of that skill?
Those people say that I'm completely wrong, and that I do not understand what a Species is. In their opinion:
"Species are only a human construction that is convenient for us humans to understand the world, but which has no special biological value."
However, I show some quotes that surely those people are unaware:
"The appearance of sexual reproduction i.e., syngamy, genetic recombination and meiosis has long been considered a major evolutionary threshold, giving rise to a fundamental increase in variation (Schopf et al. 1973), a novel ability to remove deleterious mutations (Muller 1964), and indeed ‘‘true’’ species and speciation (Stanley 1975). The presence of at least two distinct spore-producing phases in Bangiomorpha, and their close comparison to sexual phases in modern Bangia, presents a convincing case for eukaryotic sex by at least ca. 1200 Ma." - in Bangiomorpha pubescens n. gen., n. sp.: implications for the evolution of sex, multicellularity, and the Mesoproterozoic/ Neoproterozoic radiation of eukaryotes
and another one:
"Sexual reproduction predominates among organisms mainly because most evolutionary change is concentrated in speciation events, and asexual species cannot speciate in the normal sense. Asexual clones seldom diversify rapidly enough to overcome normal rates of extinction. In contrast, phylogenetic groups of sexual species (clades) commonly develop broad, heterogeneous adaptive zones rapidly enough to ensure survival." - in Clades versus clones in evolution: why we have sex
and last but not least:
"For over a century, the paradigm has been that sex invariably increases genetic variation, despite many renowned biologists asserting that sex decreases most genetic variation. Sex is usually perceived as the source of additive genetic variance that drives eukaryotic evolution vis-à-vis adaptation and Fisher's fundamental theorem. However, evidence for sex decreasing genetic variation appears in ecology, paleontology, population genetics, and cancer biology. The common thread among many of these disciplines is that sex acts like a coarse filter, weeding out major changes, such as chromosomal rearrangements (that are almost always deleterious), but letting minor variation, such as changes at the nucleotide or gene level (that are often neutral), flow through the sexual sieve." - in Sex reduces genetic variation: a multidisciplinary review

Modern mature (multiseriate) Bangia atropurpurea in transverse cross-section. A–C, Asexual/vegetative filament showing the radially arranged wedgeshaped cells. D, Portion of female plant showing the 8–16 fertilized carpospores produced by each wedgeshaped cell. E, Portion of male plant showing the ca. 128 spermatia produced by each wedge-shaped cell. Redrawn from Garbary et al. 1980.

No special biological value? Are you kidding?

An Open Letter about Natural and Sexual Selection by Rui Monteiro - 2010
The Truth about Species! - Part 1 (Why Sex)
The Truth about Species! - Part 2 (Cambrian Mystery)
The Truth about Species! - Part 3 (Inductive Nature)
The Truth about Species! - Part 4 (Entropic Nature)