"Punctuated equilibrium claims that new species arise rapidly due to accumulated Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations that get expressed during "species sorting," when populations plummet due to natural disasters, climatic changes, etc. However, new data from wild populations and molecular and analytical tools for tracing patterns of relationship and inbreeding have determined that "inbreeding depression" (decreased fitness) occurs among diverse taxa. According to the recent review:
Lukas F. Keller and Donald M. Waller. 2002. Inbreeding effects in wild populations. Trends in Ecology & Evolution 17: 230-241.
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| HELLO |
"This work reveals that levels of inbreeding depression vary across taxa, populations and environments, but are usually substantial enough to affect both individual and population performance. Data from bird and mammal populations suggest that inbreeding depression often significantly affects birth weight, survival, reproduction and resistance to disease, predation and environmental stress. Plant studies, based mostly on comparing populations that differ in size or levels of genetic variation, also reveal significant inbreeding effects on seed set, germination, survival and resistance to stress. Data from butterflies, birds and plants demonstrate that populations with reduced genetic diversity often experience reduced growth and increased extinction rates. Crosses between such populations often result in heterosis. Such a genetic rescue effect might reflect the masking of fixed Having a harmful of bad effect.deleterious Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations. Thus, it might be necessary to retain gene flow among increasingly fragmented habitat patches to sustain populations that are sensitive to inbreeding."Although the authors did not relate their study to the theory of punctuated equilibrium, it has obvious implications. Species sorting, as a mechanism of producing new species, has never been shown to be anything other than a theoretical concept. This and previous studies suggest that the only "sorting" consistently resulting from decreases in population numbers is extinction. Although this may "make room" for new species, it certainly cannot be claimed to be a creative force in evolution.
Lukas F. Keller and Donald M. Waller. 2002. Inbreeding effects in wild populations. Trends in Ecology & Evolution 17: 230-241.
And God said, Let the earth bring forth the living creature after his kind,
Genesis 1:24