Swans don't Lack heritable clutch size
- From: "John Edser" <edser@xxxxxxxxxx>
- Date: Sat, 18 Feb 2006 17:25:08 -0500 (EST)
"Perplexed in Peoria" jimmenegay@xxxxxxxxxxxxx wrote:-
Am. Nat. 167, 10.1086/499378 (2006).
(Opinion piece in Science)
ECOLOGY/EVOLUTION: Eggs on the Rise
A bird's clutch size--the quantity of eggs laid during a nesting
period--is a central feature of a bird's life history, but has
presented an evolutionary conundrum. Although studies of bird species
have predicted the existence of positive selection for increasing
clutch size over time, such increases have failed to materialize
during long-term observation, perhaps because of constraints
imposed by correlated environmental factors that also affect fitness.
JE:-
Any increase in "positive selection for increasing clutch size over time"
absolutely requires an increase in Darwinian Total Fitness: the TOTAL number
of fertile forms reproduced into one population by one parent. Just like
genes, eggs are not _independently_ selected. The fitness of each separate
egg is empirically NON additive and therefore, entirely dependent. Dependent
on what? TDF which only has one level of fitness: the fertile form level.
Clutch size can only be selected to increase if by doing so increases the
TDF of the parent/parents. This is because all parents within one population
are attempting to do just that so those that do not are inevitably selected
against. Only TDF CAN represent an empirically based _maximand_ of biology.
This is because only by maintaining TDF per Darwinian selectee per
population to artificially remain equal will all Darwinian evolution by
natural selection be halted, _empirically_, i.e. within a natural population
and not via just an "insilico" computer simulation or mathematically based
model. This can be proven by anybody anywhere by holding TDF constant within
just a simple thought experiment. Like the total number of genes the total
number of eggs simply cannot represent a maximand fitness, i.e. a total
fitness per selectee per population that is always attempting to increase.
One organism cycle begins at one fertilized egg and ends at one fertile
adult within biology (when using sex) where the organism assumption remains
utterly basic to all of biology. However, this critical cycle is
heuristically supposed to start from any point you like and finish at any
point you like within the uncorrected gene centric simplified/oversimplified
model. This allowed the number of genes to be wrongly portrayed as a
maximand because this is simply not the case, _empirically_.
In a 25-year study of mute swans, Charmantier et al. observed not
only the expected directional selection for increasing clutch size,
but also an actual increase, of 0.35 standard deviations, across
the population. Reduced predation and increased food supply over the
course of the study may have fostered the increase.
JE:-
IOW the actual increase of 0.35 standard deviations, across
the population for the number of eggs laid per _fertile_ individual required
the TDF's of each independent in fitness parent to increase and not decrease
providing a population based mean TDF increase (wherein all selective events
now remain entirely hidden). Only as long as this mean is NOT misused as a
group selective population fitness can it have a valid heuristic value.
Because the
authors kept track of the pedigrees of all of the individuals in the
study, they garnered strong evidence that these changes were genetic
rather than phenotypic, and hence that a clear microevolutionary
change took place over the course of a quarter century. -- AMS
JE:-
IMO this proves TDF to be a heritable _epistatic_ per gene, fitness.
Regards,
John Edser
Independent Researcher
edser@xxxxxxxxxx
.
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