Иванов-Петров Александр (ivanov_petrov) wrote,
Иванов-Петров Александр

Меловая революция

последняя статья на эту тему. Только если, к примеру, интересно кому-то, потому что без журналистской живинки и искринки, просто статья, однако очень хорошая

Sequence and scale of changes in the terrestrial biota during the Cretaceous (based on materials from fossil resins)
A.P. Rasnitsyn, A.S. Bashkuev, D.S. Kopylov, E.D. Lukashevich, A.G. Ponomarenko, Yu.A. Popov, D.A. Rasnitsyn, O.V. Ryzhkova, E.A. Sidorchuk, I.D. Sukatsheva, D.D. Vorontsov
Cretaceous Research 61 (2016) 234-255
a b s t r a c t
The sequence of arthropod assemblages in Cretaceous resins according to their evolutionary aspect
does not match their geological sequence. This can be only partly explained by taphonomic constraints
and inadequacy of the material: there is a deeper difference between somewhat contemporary assemblages
than was characteristic of Permian assemblages studied in a similar way in previous studies. Our
results confirm the earlier hypothesis that the PalaeozoiceMesozoic biotic crisis was not so much a mass
extinction as a biotic reorganisation that opened the way to diversification. These results might indicate a
peculiar feature of the immediate effects of such reorganisations, namely that MesozoiceCenozoic
communities became differentiated in their compositions much deeper than Palaeozoic ones (i.e., that
their constituent groups acquired the ability to evolve much deeper changes while adapting to the
ecological specifics of their environments). A transformation of organisms and/or their communities took
place, comparable in scope to the rise of skeletal fauna in the Cambrian. The difference between these
two transformations is that the later one resulted not from a particular adaptation (the skeleton) but
from the ability to specialize more deeply than was possible in the Palaeozoic.

В разделе Методика потрясающие картинки, описание там тоже отличное - что такое работа палеонтолога. Янтардах, Хатанга, Якутия, меловые янтари.




Методика в самом общем виде: определение сохранившихся членистоногих, составление списков по месторождениям. установление степени сходства месторождений, привязка к возрасту месторождений, составление списков появившихся таксонов высокого ранга (семейства), вымерших и переживших данный этап. Поправки к датировкам, поправки к таксономии, всякие тонкости - там много деталей. Методологические уточнения по поводу некоторых гипотез, связанных с минимаксными допущениями. Сделано для всех известных месторождений в мире, тут и ливанский янтарь, и испанский, и вообще весь меловой янтарь (ретиниты).

Интересный раздел - Несоответствие между возрастом и эволюционным аспектом : новый вызов для теории эволюции.
We have proposed a hypothesis (see especially
Rasnitsyn, 2012) that the PermianeTriassic biotic crisis of the biota
was not so much mass extinction as reorganization of the biota,
which opened the way to the growth of its diversity by a considerable
factor. It was not said what was the nature of this reorganization.
We still cannot say it now, but our results may indicate the
specifics of the more immediate effects of this reorganisation. They
show that post-Palaeozoic communities acquired the ability to
differ in composition more deeply under different conditions, i.e.
the taxa that constituted these communities started to change
much more deeply, adapting to the specifics of their habitats.
...The difference between the two transformations is that
the later one was not the emergence of a particular adaptation (the
skeleton) but the emergence of the ability to specialize more deeply
than was possible in the Palaeozoic. Interestingly, this effect is
equally observable in the dynamics of marine animals (Sepkoski,
1979, 1984), and thus can not be exclusive for the arthropods.
...However, these results
clearly contradict the generally accepted notions about the mechanisms
of biodiversity dynamics, in particular the notion about the
importance of extinction in general and mass extinction events in
particular (see references in Aristov and Rasnitsyn, 2015; Rasnitsyn
et al., 2015). The principal nature of this contradiction reflects the
fact that extinctions, especially mass extinctions, are logically
associated with effects of some unfavourable external (environmental)
factors, whereas it is difficult to associate changes in the
rate of diversification with anything but effects of biotic factors. One
of such factors may be a large-scale deceleration of evolution
resulting from the systemic buffering of biological organisation, or
the adaptive trade-off, defined as a “contradiction between necessity
to change and necessity to keep adaptive all of the selectively
controlled structures and functions” (see Rasnitsyn, 2015 for
details and references). The evolutionary trade-off makes a species
keep within the limits of trivial (evolutionary secure) phenotypic
diversity, even if its environment and genome are changing. Over
geological time, biota may become increasingly saturated with the
taxa having quite perfect (finely balanced) organisation, which is
difficult to change: diversification rate slows down. Such taxa
usually become extinct without leaving any progeny, and their
extinction leads to gradual depletion of the biota e the phenomenon
called a “perfection trap” (Rasnitsyn, 1989), which probably
occurred in late Permian. This situation continues until the
depleted communities and the consequently weakened biotic
control of fitness (‘erosion of perfection trap’) allows organisms to
escape the trap (Rasnitsyn, 1989, see further in 2015). As, in a finely
tuned system, one modification leads to many, explosive radiations
that we observe occur.

В результате, при учете всех данных, оказывается возможным сделать некоторые выводы.

The family-level study of the compositions of arthropod assemblages in Cretaceous ambers worldwide has revealed their outstanding diversity (a total of 502 families, including questioned identifications, have been recorded), and certain patterns in changes of their composition in space and time. The assemblages group both geographically and temporally. It is shown that the rates of extinction (disappearance of families from the fossil record) change rather weakly over the studied interval, so that the dynamics of diversity, which is positive almost at every stage (the total diversity increases), is determined by much larger oscillations in the rate of emergence of new families (their appearance in the fossil record). This indicates the minor role played by extinction events and, thus, by unfavourable external influences, and the major role played by internal, biotic changes. Adaptive trade-off and the ‘perfection trap’ as its consequence may constitute such a biotic factor, slowing down the renewal of the biota.

The rates of renewal for the composition of families (dynamics of the proportion of families of young and ancient cohorts) have proved dramatically different in different assemblages, indicating the lack of significant correlation between their evolutionary aspect and their age, in contrast to what was revealed earlier about the Palaeozoic interval of insect evolution. Taking into account also other differences in biodiversity dynamics between the Palaeozoic and Mesozoic, this asynchronicity of renewal of Cretaceous amber assemblages can be explained by the ability of Mesozoic arthropod communities to become more deeply specialized for particular environments, an ability that evolved in the course of the reorganization of the biota at the PalaeozoiceMesozoic boundary.

Еще раз, мой краткий пересказ: данные указывают скорее не на массовое вымирание, связанное с какой-либо внешней причиной, а на перестройку сообществ, вызванную внутренними, биотическими причинами. [[Метеоритам нет, системным причинам - да}} При этом обнаружены занятные эффекты несоответствия возраста и того, что можно назвать эволюционной продвинутостью. Что опять указывает на внутренние эффекты специализации, которые сильно искажают "линейные" возрастные эффекты. Но это уже мой пересказ, с использованием метафор и неизбежными упрощениями.
Tags: biology4
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