Xref: utzoo sci.bio:976 soc.men:3012
Newsgroups: sci.bio,soc.men
Path: utzoo!jackson
From: jackson@utzoo.uucp (Don Jackson)
Subject: Re: sexual selection and investment
Message-ID: <1988Mar13.160941.22096@utzoo.uucp>
Organization: U of Toronto Zoology
Date: Sun, 13 Mar 88 16:09:41 GMT


Richard Harter (25442@cca.CCA.COM) writes:

>NOTE THAT IT IS THE FEMALE THAT SELECTS.  Females select, fundamentally,
>because they make the big investment in offspring.

This is true as a generalization. However, there are countless numbers of
species where the investment by the male is equal to or exceeds the female.
Numerous species of fish reproduce in nests formed by the male and guarded
by males after spawning. The greater costs (e.g. energy) incurred by the male
(in terms of reduced growth and increased mortality) appear to counter
your argument that females have the greater investment. 

There may be natural selection against distinctive females through
increased risk of predation. An example of this is the Guppy (Poecilia
reticulata) where coloration increases predation. Therefore, dull
females have greater fitness than colorful females. However, sexual
selection may favour brightly colored males provided the benefits derived
from their coloration are greater than the increased costs associated with
predation.

Trying to distinguish between different types of selection (e.g. natural
versus sexual) is a matter of semantics. The process implies that,
on average, some trait (e.g. color, larger tail, etc.) results in a greater
fitness (i.e. more progeny) than a similar organism lacking that trait.
-- 
Name:   Don Jackson
Mail:   Dept. Zoology, Univ. Toronto
        Toronto, Ontario, Canada    M5S 1A1
UUCP:   {allegra,ihnp4,linus,decvax}!utzoo!jackson