scholarly journals Colonial ascidians strongly preyed upon, yet dominate the substrate in a subtropical fouling community

2019 ◽  
Author(s):  
Laurel Sky Hiebert ◽  
Edson A. Vieira ◽  
Gustavo M. Dias ◽  
Stefano Tiozzo ◽  
Federico D. Brown
Keyword(s):  
Life Histories ◽  
Interactive Effects ◽  
Fouling Communities ◽  
Colonial Species ◽  
Eastern Brazil ◽  
Low Latitudes ◽  
Predation Treatment ◽  
The Tropics ◽  
Colonial Ascidians ◽  
Solitary Species

AbstractHigher diversity and dominance at lower latitudes has been suggested for colonial species. We verified the latitudinal pattern in species richness of ascidians, finding that higher colonial-to-solitary species ratios occur in the tropics and subtropics. At the latitudinal region with the highest ratio, in south-eastern Brazil, we confirmed that colonial species dominate the space on artificial plates in two independent studies of five fouling communities. We manipulated settlement plates to measure effects of predation and competition on growth and survivorship of colonial vs. solitary ascidians. Eight ascidian species were subjected to a predation treatment, i.e. caged vs. exposed to predators, and a competition treatment, i.e. leaving vs. removing competitors, to assess main and interactive effects. Predation had a greater effect on growth and survivorship of colonial compared to solitary species, whereas competition did not show consistent patterns between the two life histories. We hypothesize that colonial ascidians dominate at this subtropical site despite being highly preyed upon because they regrow when partially consumed and can adjust in shape and space to grow into refuges. We contend that these means of avoiding mortality from predation can have large influences on the diversification patterns of colonial species at low latitudes, where predation intensity is greater.

scholarly journals Colonial ascidians strongly preyed upon, yet dominate the substrate in a subtropical fouling community

2019 ◽  
Vol 286 (1899) ◽  
pp. 20190396 ◽  
Author(s):  
Laurel Sky Hiebert ◽  
Edson A. Vieira ◽  
Gustavo M. Dias ◽  
Stefano Tiozzo ◽  
Federico D. Brown
Keyword(s):  
Interactive Effects ◽  
Southeastern Brazil ◽  
Fouling Communities ◽  
Colonial Species ◽  
Predation Intensity ◽  
Low Latitudes ◽  
Predation Treatment ◽  
The Tropics ◽  
Colonial Ascidians ◽  
Solitary Species

Higher diversity and dominance at lower latitudes has been suggested for colonial species. We verified this pattern in species richness of ascidians, finding that higher colonial-to-solitary species ratios occur in the tropics and subtropics. At the latitudinal region with the highest ratio, in southeastern Brazil, we confirmed that colonial species dominate space on artificial plates in two independent studies of five fouling communities. We manipulated settlement plates to measure effects of predation and competition on growth and survivorship of colonial versus solitary ascidians. Eight species were subjected to a predation treatment, i.e. caged versus exposed to predators, and a competition treatment, i.e. leaving versus removing competitors, to assess main and interactive effects. Predation had a greater effect on growth and survivorship of colonial compared to solitary species, whereas competition did not show consistent patterns. We hypothesize that colonial ascidians dominate at this subtropical site despite being highly preyed upon because they regrow when partially consumed and can adjust in shape and space to grow into refuges. We contend that these means of avoiding mortality from predation can have large influences on diversification patterns of colonial species at low latitudes, where predation intensity is greater.

scholarly journals Obliquity forcing of low-latitude climate

2015 ◽  
Vol 11 (1) ◽  
pp. 221-241 ◽  
Author(s):  
J. H. C. Bosmans ◽  
F. J. Hilgen ◽  
E. Tuenter ◽  
L. J. Lourens
Keyword(s):  
High Latitude ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Rotational Axis ◽  
Low Latitude ◽  
Low Latitudes ◽  
Paleoclimate Records ◽  
Induced Changes ◽  
The Tropics

Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical paleoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, implying that this gradient may be used to explain obliquity signals in low-latitude paleoclimate records instead of the classic 65° N summer insolation curve.

Evolutionary conservatism will limit responses to climate change in the tropics

2021 ◽  
Vol 17 (10) ◽  
Author(s):  
Ethan B. Linck ◽  
Benjamin G. Freeman ◽  
C. Daniel Cadena ◽  
Cameron K. Ghalambor
Keyword(s):  
Thermal Tolerance ◽  
Species Turnover ◽  
Tropical Species ◽  
Evolutionary Divergence ◽  
Closely Related Species ◽  
Tropical Mountains ◽  
Low Latitudes ◽  
Parapatric Speciation ◽  
The Tropics

Rapid species turnover in tropical mountains has fascinated biologists for centuries. A popular explanation for this heightened beta diversity is that climatic stability at low latitudes promotes the evolution of narrow thermal tolerance ranges, leading to local adaptation, evolutionary divergence and parapatric speciation along elevational gradients. However, an emerging consensus from research spanning phylogenetics, biogeography and behavioural ecology is that this process rarely, if ever, occurs. Instead, closely related species typically occupy a similar elevational niche, while species with divergent elevational niches tend to be more distantly related. These results suggest populations have responded to past environmental change not by adapting and diverging in place, but instead by shifting their distributions to tightly track climate over time. We argue that tropical species are likely to respond similarly to ongoing and future climate warming, an inference supported by evidence from recent range shifts. In the absence of widespread in situ adaptation to new climate regimes by tropical taxa, conservation planning should prioritize protecting large swaths of habitat to facilitate movement.

scholarly journals Obliquity forcing of low-latitude climate

2015 ◽  
Vol 11 (10) ◽  
pp. 1335-1346 ◽  
Author(s):  
J. H. C. Bosmans ◽  
F. J. Hilgen ◽  
E. Tuenter ◽  
L. J. Lourens
Keyword(s):  
High Latitude ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Rotational Axis ◽  
Tropical Circulation ◽  
Low Latitude ◽  
Low Latitudes ◽  
Induced Changes ◽  
The Tropics

Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two idealized experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, suggesting that this gradient may be used to explain obliquity signals in low-latitude palaeoclimate records instead of the classical 65° N summer insolation curve.

scholarly journals Climate change, transgenic corn adoption and field-evolved resistance in corn earworm

2017 ◽  
Vol 4 (6) ◽  
pp. 170210 ◽  
Author(s):  
P. Dilip Venugopal ◽  
Galen P. Dively
Keyword(s):  
Climate Change ◽  
Pest Management ◽  
Life Histories ◽  
Helicoverpa Zea ◽  
Temperature Anomaly ◽  
Corn Earworm ◽  
Interactive Effects ◽  
Agricultural Pest ◽  
Bt Resistance ◽  
Increased Temperature

Increased temperature anomaly during the twenty-first century coincides with the proliferation of transgenic crops containing the bacterium Bacillus thuringiensis (Berliner) (Bt) to express insecticidal Cry proteins. Increasing temperatures profoundly affect insect life histories and agricultural pest management. However, the implications of climate change on Bt crop–pest interactions and insect resistance to Bt crops remains unexamined. We analysed the relationship of temperature anomaly and Bt adoption with field-evolved resistance to Cry1Ab Bt sweet corn in a major pest, Helicoverpa zea (Boddie). Increased Bt adoption during 1996–2016 suppressed H. zea populations, but increased temperature anomaly buffers population reduction. Temperature anomaly and its interaction with elevated selection pressure from high Bt acreage probably accelerated the Bt-resistance development. Helicoverpa zea damage to corn ears, kernel area consumed, mean instars and proportion of late instars in Bt varieties increased with Bt adoption and temperature anomaly, through additive or interactive effects. Risk of Bt-resistant H. zea spreading is high given extensive Bt adoption, and the expected increase in overwintering and migration. Our study highlights the challenges posed by climate change for Bt biotechnology-based agricultural pest management, and the need to incorporate evolutionary processes affected by climate change into Bt-resistance management programmes.

scholarly journals Evolutionary determinants of morphological polymorphism in colonial animals

2016 ◽  
Author(s):  
Carl Simpson ◽  
Jeremy B.C. Jackson ◽  
Amalia Herrera-Cubilla
Keyword(s):  
Life Histories ◽  
Competitive Ability ◽  
Environmental Variability ◽  
Temporal Position ◽  
Costs And Benefits ◽  
Isthmus Of Panama ◽  
Modular Units ◽  
Environmental Hypothesis ◽  
Colonial Ascidians

AbstractColonial animals commonly exhibit morphologically polymorphic modular units that are phenotypically distinct and specialize in specific functional tasks. But how and why these polymorphic modules have evolved is poorly understood. Across colonial invertebrates there is wide variation in the degree of polymorphism from none in colonial ascidians, to extreme polymorphism in siphonophores such as the Portuguese Man of War. Bryozoa are a phylum of exclusively colonial invertebrates that uniquely exhibit almost the entire range of polymorphism from monomorphic species to others that rival siphonophores in their polymorphic complexity. Previous approaches to understanding the evolution of polymorphism have been based upon analyses of (1) the functional role of polymorphs or (2) presumed evolutionary costs and benefits based upon evolutionary theory that postulates polymorphism should only be evolutionarily sustainable in more “stable” environments because polymorphism commonly leads to the loss of feeding and sexual competence. Here we use bryozoans from opposite shores of the Isthmus of Panama to revisit the environmental hypothesis by comparison of faunas from distinct oceanographic provinces that differ greatly in environmental variability and we then examine the correlations between the extent of polymorphism in relation to patterns of ecological succession and variation in life histories. We find no support for the environmental hypothesis. Distributions of the incidence of polymorphism in the oceanographically unstable Eastern Pacific are indistinguishable from those in the more stable Caribbean. In contrast, the temporal position of species in a successional sequence is collinear with the degree of polymorphism because species with fewer types of polymorphs are competitively replaced by species with higher numbers of polymorphs on the same substrata. Competitively dominant species also exhibit patterns of growth that increase their competitive ability. The association between degrees of polymorphism and variations in life histories is fundamental to understanding of the macroevolution of polymorphism.

Aphid–Buchnera–Ant symbiosis; or why are aphids rare in the tropics and very rare further south?

2016 ◽  
Vol 107 (2-3) ◽  
pp. 297-310 ◽  
Author(s):  
Evgeny Perkovsky ◽  
Piotr Wegierek
Keyword(s):  
Northern Hemisphere ◽  
Late Cretaceous ◽  
Buchnera Aphidicola ◽  
Ant Colonies ◽  
Ant Predation ◽  
Low Latitudes ◽  
Extinction Event ◽  
Steep Decline ◽  
Cretaceous Terrestrial Revolution ◽  
The Tropics

ABSTRACTAt least since the Cretaceous Terrestrial Revolution, the geographical distribution of aphids, particularly in the Northern Hemisphere, has been strongly affected by the low thermal tolerance of their obligatory bacterial symbiont, Buchnera aphidicola, which was why the aphids switched to obligate parthenogenesis in low latitudes. Hormaphidids and greenideids penetrated into the tropics only after the Oligocene strengthening of climate seasonality, and specialisations of the tropical representatives of these families did not allow them to spread further south (in the case of cerataphidines), or only allowed in few cases (in the case of greenideids).Aphids suffered from the Mesozoic–Cenozoic boundary extinction event much more strongly than other insects. The extinction was roughly coincidental with the establishment of the tight symbiosis of aphids with formicine and dolichoderine ants, which was accompanied by the flourishing of all three groups.In the Cretaceous, all of the representatives of extant and subfamilies occupied positions that were subordinate to Armaniinae and Sphecomyrminae. Prior to large ant colonies evolving their efficient ant–aphid mutualism, the aphids remained unprotected before the growing ant predation. The origin of the aphid trophobiosis with large colonies of Formicinae and Dolichoderinae has resulted in the steep decline of aphids left beyond that ant–aphid symbiotic network. By at least the basal Eocene (unlike the Late Cretaceous), ant proportions in the entomofauna increased sharply, and evident dominants emerged. Even now, aphid milkers from small colonies (hundreds of specimens) never protect their symbionts, and homopteran-tending ants are more likely to be dominant, with large colonies of 104–105 workers.The mutualistic ant–aphid system failed to cross the tropical belt during the Cenozoic because of Buchnera's low heat tolerance. As a result, the native southern temperate aphid fauna consists now of seven genera only, five of which are Late Cretaceous relicts. Some of them had relatives in Late Cretaceous amber of the Northern Hemisphere.

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