Hasil untuk "Evolution"

M. Lynch

E. Domingo, J. Sheldon, C. Perales

M. Araújo, F. Ferri‐Yáñez, F. Bozinovic et al.

Climate change is altering phenology and distributions of many species and further changes are projected. Can species physiologically adapt to climate warming? We analyse thermal tolerances of a large number of terrestrial ectotherm (n = 697), endotherm (n = 227) and plant (n = 1816) species worldwide, and show that tolerance to heat is largely conserved across lineages, while tolerance to cold varies between and within species. This pattern, previously documented for ectotherms, is apparent for this group and for endotherms and plants, challenging the longstanding view that physiological tolerances of species change continuously across climatic gradients. An alternative view is proposed in which the thermal component of climatic niches would overlap across species more than expected. We argue that hard physiological boundaries exist that constrain evolution of tolerances of terrestrial organisms to high temperatures. In contrast, evolution of tolerances to cold should be more frequent. One consequence of conservatism of upper thermal tolerances is that estimated niches for cold-adapted species will tend to underestimate their upper thermal limits, thereby potentially inflating assessments of risk from climate change. In contrast, species whose climatic preferences are close to their upper thermal limits will unlikely evolve physiological tolerances to increased heat, thereby being predictably more affected by warming.

M. Kirkpatrick, N. Barton

L. Welch, R. Luostarinen

G. Wray, Matthew W. Hahn, E. Abouheif et al.

J. Doebley, A. Stec, L. Hubbard

Wen-Hsiung Li, D. Graur

R. Boyd, P. Richerson

E. Carmines, J. Stimson

M. Riley, J. Wertz

P. Hedrick

P. Bak, K. Sneppen

J. Gillespie

N. Ellstrand, K. Schierenbeck

D. Clayton

B. Moore, N. Katz, G. Lake et al.

NEARBY clusters of galaxies are filled with red elliptical 'E' and lenticular 'SO' galaxies1, while younger clusters (at redshifts of ≳ 0.4) contain substantial populations of blue spiral galaxies with morphological peculiarities2–7 (see Fig. 1). Thus, within the last 4–5 billion years, galaxies in clusters underwent strong evolution that completely changed their character. By contrast, galaxies that are not associated with clusters show far less morphological evolution8. Here we propose that multiple highspeed encounters between galaxies—'galaxy harassment'— drives the morphological evolution in clusters. Our simulations show that these encounters are very different from mergers; they transform small disk galaxies into dwarf elliptical or dwarf spheroidal galaxies. Harassment will leave detectable debris arcs and could provide fuel for quasars in sub-luminous host galaxies.

D. Stern

E. MacLean, Brian Hare, C. Nunn et al.

Significance Although scientists have identified surprising cognitive flexibility in animals and potentially unique features of human psychology, we know less about the selective forces that favor cognitive evolution, or the proximate biological mechanisms underlying this process. We tested 36 species in two problem-solving tasks measuring self-control and evaluated the leading hypotheses regarding how and why cognition evolves. Across species, differences in absolute (not relative) brain volume best predicted performance on these tasks. Within primates, dietary breadth also predicted cognitive performance, whereas social group size did not. These results suggest that increases in absolute brain size provided the biological foundation for evolutionary increases in self-control, and implicate species differences in feeding ecology as a potential selective pressure favoring these skills. Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.

Gaoang Wang, Sitao Zhu, Fuxing Jiang et al.

Abstract Ultra-thick soft-hard (UTSH) composite coal seams, composed of alternating layers of soft and hard coal, frequently experience severe rockburst accidents during roadway excavation under shallow burial depths (< 500 m). However, research on the mechanisms underlying such rockbursts remains limited. This study simulates the failure process of surrounding rock in roadways excavated through UTSH composite coal seams under shallow depth conditions using true triaxial low axial pressure unloading tests. Through a comprehensive analysis of failure characteristics, mechanical properties, and acoustic emission (AE) parameters of soft coal, hard coal, and multi-layered soft-hard coal composite specimens (2–4 alternating layers), the mechanism of rockburst induced by excavation unloading in shallow depths UTSH composite coal seams is revealed. Results demonstrate that under low axial pressure unloading conditions, composite specimens exhibit higher crack quantities and lengths compared to the hard coal specimen, with energy accumulation ranging from 70.2 to 120.7 kJ/m3, significantly exceeding the 66.6 kJ/m3 observed in the hard coal specimen. AE parameters further confirm that composite specimens undergo more severe damage than the hard coal specimen. A three-stage failure mechanism is proposed: (1) low-stress shear failure in soft coal layers, (2) interface shear failure induced by concentrated stress, and (3) shear failure in hard coal layers caused by stress transfer. This sequential process explains rockburst occurrences in shallow depths of composite coal seams, and a mechanical criterion is established accordingly. The findings provide theoretical foundations for monitoring, early warning, and prevention of rockburst hazards in roadways excavated through UTSH composite coal seams.