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Механізми трансформації структур
черепа в еволюції
нічниць та споріднених груп гладконосих рукокрилих
Дзеверін Ігор Ігорович
дисертація на здобуття наукового ступеню доктора біологічних
наук
Офіційні опоненти: Рековець Леонід Іванович,
Волох Анатолій Михайлович, Токарський Віктор Арсентійович.
спеціальність 03.00.08 — зоологія;
захист: 07.02.2012 в Інституті зоології ім. І. І. Шмальгаузена
НАН України (спеціалізована вчена рада Д 26.153.01).
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Дзеверін І. І. Механізми трансформації структур черепа
в еволюції нічниць та споріднених груп гладконосих рукокрилих.
– Рукопис. – Дисертація на здобуття наукового ступеня
доктора біологічних наук за спеціальністю 03.00.08 – зоологія.
– Інститут зоології ім. І. І. Шмальгаузена НАН України.
– Київ, 2011.
На вибірці з 410-и екз. досліджено внутрішньовидову
мінливість та міжвидові відмінності десяти видів роду
Myotis за краніометричними ознаками, одержано
кількісні оцінки масштабів та темпів дивергенції, проведено
порівняння характеристик еволюції в різних групах гладконосих
кажанів та ссавців загалом. Темпи трансформації краніометричних
ознак зазнавали в нічниць змін під час еволюції, однак
не перевищували певного рівня, що міг бути забезпечений
рушійним добором помірної інтенсивності або генетичним
дрейфом. Консерватизм скелетних структур в еволюції рукокрилих
є наслідком дії стабілізуючого добору, а не структурних
обмежень. Регресивні трансформації в еволюції досліджених
структур швидше спричинено нагромадженням мутацій, ніж
негативним добором. Запропоновано математичну модель регресивної
еволюції, що ґрунтується на еволюційній концепції І. І.
Шмальгаузена.
Ключові слова: Myotis, Vespertilionidae,
Mammalia, череп, кількісна ознака, еволюція, дивергенція,
стазис, природний добір, генетичний дрейф, адаптація,
гетерохронія, рудимент.
Dzeverin, I. I. Mechanisms affecting the evolutionary
change of cranial structures in Myotis and related
vespertilionid taxa. – Manuscript. – Thesis for obtaining
the degree of Doctor of Sciences (Biology) in specialty
03.00.08 – zoology. – Kiev, 2011.
Multiple craniometric variation as well
as evolutionary rates and patterns were studied in 10
extant Palearctic Myotis species (13 OTUs) on
a total sample of 410 specimens. Several additional samples
from various mammalian taxa were taken for comparison.
Lynch’s and Gingerich’s approaches were combined to evaluate
the univariate rates of divergence. Squared Mahalanobis
distance was used as a multivariate measure for amount
of divergence, and squared Mahalanobis distance weighted
by time was used as a measure for the rate of divergence.
Rates of divergence were measured for
27 craniometric characters in 12 extant OTUs from the
bat genus Myotis (Chiroptera, Vespertilionidae).
The obtained estimates were found to be consistent with
random walk hypothesis. Thus the divergence in Myotis
could be guided by random drift and mutations. The high
dispersion in rate estimates suggests also a possible
input of randomly fluctuating selection. Size-adjusted
data appeared to be lesser then the initial data, and
it can be concluded that both size and shape were involved
in divergence of Myotis species. The skeletal
characters in bats are known to be extremely conservative
during long-term evolution, however the possibility for
random walk at short time interval implies that bat evolution
is constrained rather ecologically and biomechanically
than genetically or developmentally.
In five closely related OTUs namely M.
myotis, M. blythii oxygnathus, M. b. omari, M. b. blythii,
and M. nattereri, the estimates for evolutionary
rates were found to be lower than expected if the divergence
had been produced solely by mutation and random drift.
So, it can be concluded that stabilizing selection was
the principal factor that maintained craniometric characters
during the evolution of the studied species and prevented
their greater diversification. Moreover, the rates of
divergence between the ancestors of M. nattereri and the
common ancestors of M. blythii and M. myotis
apparently were higher than the rates of following
divergence between M. myotis, M. b. oxygnathus, M.
b. omari and M. b. blythii. All the observed
differences between the studied OTUs could be established
by random drift or directional selection of rather moderate
intensity. The multivariate analysis indicated that Crimean
M. blythii are the specimens of M. b. oxygnathus
and confirmed that the isolated population of M. blythii
from Altai (the 13th studied OTU), which has been recently
described as the subspecies M. b. altaicus, really
differs from all the other known Myotis taxa.
The regressive transformations in skull
evolution result from accumulation of random mutations
more likely than from negative selection. A mathematical
model for the regressive trend of complex structures in
neutral evolution is developed. It is based on Schmalhausen’s
evolutionary concept. Evolutionary changes of characters
formed in ontogeny by developmental induction are modeled
for an infinite population and for replicate finite populations
under a mutation – drift equilibrium. Induction occurs
by interaction of reactants, which must therefore coincide
in time intervals of their abilities to react. This mechanism
is being damaged in evolution of useless structures by
random mutations in genes that control simultaneous formations
of reactants, whereas mutational effects on important
structures are restrained by selection. The breakdown
of induction mechanisms produces increased variability
and degeneration in vestigial characters. Quantitative
estimations are illustrated by data regarding regressive
trends in some groups of mammals. Time spans sufficient
for complete loss of vestigial organs obtained from the
modelings are much smaller than the periods of macroevolutionary
changes. Certain functional value and the genetic correlation
with important structures are the most probable mechanisms
that could prevent the rapid loss of vestigial structures.
Key words: Myotis, Vespertilionidae,
Mammalia, skull, quantitative character, evolution, divergence,
stasis, natural selection, genetic drift, adaptation,
heterochrony, vestigial organ.
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