Adeptos a la Adaptación: tres propuestas clasicas para la arqueología y una evaluación
Published in Revista Antípoda 13, December 2011
In Spanish
Thirty years after Kirch (1980) seminal paper, this work reviews the role of adaptation in contemporary archaeological... more Thirty years after Kirch (1980) seminal paper, this work reviews the role of adaptation in contemporary archaeological thought and discusses its use. In this process, the use of this concept in biology will be examined as well as its use in archaeology, as it is incorporated in processualism, selectionism and Dual Inheritance theories. The author concludes with an evaluation of its current potential.
The temporal dynamics of resource use by frugivorous birds: a network approach.
published in Ecology
Ecological networks patterns are influenced by a diverse array of ecological processes that operate at different... more Ecological networks patterns are influenced by a diverse array of ecological processes that operate at different temporal scales. Here we analyzed if the coupled effect of local abundance variation, seasonally phenotypic plastic responses and species evolutionary adaptations might act in concert to shape network patterns. We studied the temporal variation in three interaction properties of bird species (number of interactions per species, interaction strength and asymmetry) in a temporal sequence of 28 plant-frugivore interaction networks spanning two years in a Mediterranean scrub community. Three main hypotheses dealing with the temporal variation of networks properties were tested, examining the effects of abundance, switching behaviour between alternative resources and morphological traits in determining consumer interaction patterns. Our results demonstrate that temporal variation in consumer interaction patterns is explained by short-term variation in resource and bird abundances and seasonal dietary switches between alternative resources (fleshy fruits and insects). Moreover, differences in beak morphology are associated with differences in switching behaviour between resources, suggesting an important role of foraging adaptations in determining network patterns. We argue that beak shape adaptations might determine generalist and specialist feeding behaviours and thus the positions of consumer species within the network. Finally, we provide a preliminary framework to interpret phylogenetic signal in plant-animal networks. Indeed, we show that the strength of the phylogenetic signal in networks depends on the relative importance of abundance, behavioural and morphological variables. We show that these variables strongly differ in their phylogenetic conservatism. Consequently, we suggest that moderate and significant phylogenetic effects should be commonly observed in networks.
57 views
Seen by:Switching behavior, coexistence and diversification: comparing empirical community-wide evidence with theoretical predictions
published in Ecology Letters
A primary goal for ecologists is the identification of the structures and processes that generate diversity in natural... more A primary goal for ecologists is the identification of the structures and processes that generate diversity in natural communities. Theory shows that behavioral switching between two alternative resources can increase diversity, both by enhancing species coexistence and increasing lineage diversification in mathematical models. However, an empirical demonstration of the community-wide patterns of switching predicted by this theory is still lacking. Here we evaluate the nature of switching behavior between two alternative resource channels, invertebrates and fruits, in a Mediterranean scrubland bird community. We also examine morphological differences in a trait related to the use of these channels. Our results are the first community-wide empirical evidence showing that different patterns of resource switching that correlate with morphological differences characterize a group of potentially competing species. These patterns are consistent with theoretical predictions, suggesting a possible role of switching behavior in promoting avian coexistence and diversification.
43 views
Seen by:Dating the fungus-growing termites’ mutualism shows a mixture between ancient codiversification and recent symbiont dispersal across divergent hosts
by Tania Nobre
Co-authored with:
N. A. KONÉ, S. KONATÉ2, K. E. LINSENMAIR, D. K. AANEN
The mutualistic symbiosis between fungus-growing termites and Termitomyces fungi originated in Africa and shows a... more The mutualistic symbiosis between fungus-growing termites and Termitomyces fungi originated in Africa and shows a moderate degree of interaction specificity. Here we estimate the age of the mutualism and test the hypothesis that the major splits have occurred simultaneously in the host and in the symbiont. We present a scenario where fungus-growing termites originated in the African rainforest just before the expansion of the savanna, about 31 Ma (19–49 Ma). Whereas rough age correspondence is observed for the four main clades of host and symbiont, the analysis reveals several recent events of host switching followed by dispersal of the symbiont throughout large areas and throughout different host genera. The most spectacular of these is a group of closely related fungi (the maximum age of which is estimated to be 2.4 Ma), shared between the divergent genera Microtermes, Ancistrotermes, Acanthotermes and Synacanthotermes (which diverged at least 16.7 Ma), and found throughout the African continent and on Madagascar. The lack of geographical differentiation of fungal symbionts shows that continuous exchange has occurred between regions and across host species.
Farming termites determine the genetic population structure of Termitomyces fungal symbionts
by Tania Nobre
Co-authored with:
C. FERNANDES, J. J. BOOMSMA, J. KORB, D. K. AANEN
Symbiotic interactions between macrotermitine termites and their fungal symbionts have a moderate degree of... more Symbiotic interactions between macrotermitine termites and their fungal symbionts have a moderate degree of specificity. Consistent with horizontal symbiont transmission, host switching has been frequent over evolutionary time so that single termite species can often be associated with several fungal symbionts. However, even in the few termite lineages that secondarily adopted vertical symbiont transmission, the fungal symbionts are not monophyletic. We addressed this paradox by studying differential transmission of fungal symbionts by alate male and female reproductives, and the genetic population structure of Termitomyces fungus gardens across 74 colonies of Macrotermes bellicosus in four west and central African countries. We confirm earlier, more limited, studies showing that the Termitomyces symbionts of M. bellicosus are normally transmitted vertically and clonally by dispersing males. We also document that the symbionts associated with this termite species belong to three main lineages that do not constitute a monophyletic group. The most common lineage occurs over the entire geographical region that we studied, including west, central and southern Africa, where it is also associated with the alternative termite hosts Macrotermes subhyalinus and Macrotermes natalensis. While Termitomyces associated with these alternative hosts are horizontally transmitted and recombine freely, the genetic population structure of the same Termitomyces associated with M. bellicosus is consistent with predominantly clonal reproduction and only occasional recombination. This implies that the genetic population structure of Termitomyces is controlled by the termite host and not by the Termitomyces symbiont.
Recovery from the most profound mass extinction of all time
by Sarda Sahney
Sahney, S. and M.J. Benton 2008. Recovery from the most profound mass extinction of all time. Proceedings of The Royal Society of London. Series B, Biological Sciences 275:759-765.
The end-Permian mass extinction, 251 million years (Myr) ago, was the most devastating ecological event of all time,... more The end-Permian mass extinction, 251 million years (Myr) ago, was the most devastating ecological event of all time, and it was exacerbated by two earlier events at the beginning and end of the Guadalupian, 270 and 260 Myr ago. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. Disaster taxa, such as Lystrosaurus, insinuated themselves into almost every corner of the sparsely populated landscape in the earliest Triassic, and a quick taxonomic recovery apparently occurred on a global scale. However, close study of ecosystem evolution shows that true ecological recovery was slower. After the end-Guadalupian event, faunas began rebuilding complex trophic structures and refilling guilds, but were hit again by the end-Permian event. Taxonomic diversity at the alpha (community) level did not recover to pre-extinction levels; it reached only a low plateau after each pulse and continued low into the Late Triassic. Our data showed that though there was an initial rise in cosmopolitanism after the extinction pulses, large drops subsequently occurred and, counter-intuitively, a surprisingly low level of cosmopolitanism was sustained through the Early and Middle Triassic.
Links between global taxonomic diversity, ecological diversity and the expansion of vertebrates on land
by Sarda Sahney
Sahney, S., Benton, M.J. and Paul A. Ferry 2010. Links between global taxonomic diversity, ecological diversity and the expansion of vertebrates on land. Biology Letters. 6:544-547
Tetrapod biodiversity today is great; over the past 400 Myr since vertebrates moved onto land, global tetrapod... more Tetrapod biodiversity today is great; over the past 400 Myr since vertebrates moved onto land, global tetrapod diversity has risen exponentially, punctuated by losses during major extinctions. There are links between the total global diversity of tetrapods and the diversity of their ecological roles, yet no one fully understands the interplay of these two aspects of biodiversity and a numerical analysis of this relationship has not so far been undertaken. Here we show that the global taxonomic and ecological diversity of tetrapods are closely linked. Throughout geological time, patterns of global diversity of tetrapod families show 97 per cent correlation with ecological modes. Global taxonomic and ecological diversity of this group correlates closely with the dominant classes of tetrapods (amphibians in the Palaeozoic, reptiles in the Mesozoic, birds and mammals in the Cenozoic). These groups have driven ecological diversity by expansion and contraction of occupied ecospace, rather than by direct competition within existing ecospace and each group has used ecospace at a greater rate than their predecessors.
277 views
Seen by: and 29 moreRainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica
by Sarda Sahney
Sahney, S., Benton, M.J. & Falcon-Lang, H.J. 2010 Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica. Geology. 38: 1079-1082.
Abrupt collapse of the tropical rainforest biome (Coal Forests) drove rapid diversification of Carboniferous tetrapods... more Abrupt collapse of the tropical rainforest biome (Coal Forests) drove rapid diversification of Carboniferous tetrapods (amphibians and reptiles) in Euramerica. This finding is based on analysis of global and alpha diversity databases in a precise geologic context. From Visean to Moscovian time, both diversity measures steadily increased, but following rainforest collapse in earliest Kasimovian time (ca. 305 Ma), tetrapod extinction rate peaked, alpha diversity imploded, and endemism developed for the first time. Analysis of ecological diversity shows that rainforest collapse was also accompanied by acquisition of new feeding strategies (predators, herbivores), consistent with tetrapod adaptation to the effects of habitat fragmentation and resource restriction. Effects on amphibians were particularly devastating, while amniotes ('reptiles') fared better, being ecologically adapted to the drier conditions that followed. Our results demonstrate, for the first time, that Coal Forest fragmentation influenced profoundly the ecology and evolution of terrestrial fauna in tropical Euramerica, and illustrate the tight coupling that existed between vegetation, climate, and trophic webs.
248 views
Seen by: and 17 moreThe global distribution of net primary production: resolving the paradox
Huston & Wolverton 2009
The distribution of the diversity and abundance of life on Earth is thought to be shaped by the patterns of plant... more The distribution of the diversity and abundance of life on Earth is thought to be shaped by the patterns of plant growth (net primary production, NPP) in the oceans and on land. The well-known latitudinal gradient of species diversity reaches its maximum in tropical rain forests, which are considered to be the most productive ecosystems on the planet. However, this high tropical productivity on land is the opposite of the well-documented distribution of marine productivity, which is greatest in the high-latitude oceans around the poles. This paradox can be resolved by a reevaluation of the terrestrial productivity gradient. Compilations of direct measurements of forest NPP show that annual NPP in tropical forests is no different than annual NPP in temperate forests, contrary to recent syntheses and to the output of global vegetation models. Other properties of forest ecosystems, such as basal area of trees, wood density, and the ratio of wood to leaf production, as well as animal properties such as body size, population density, and reproductive rates, support the conclusion that ecologically relevant terrestrial productivity is actually highest in the temperate latitudes, reaching a maximum between 30° and 50° before declining toward the poles. This “reversal” of the latitudinal productivity gradient, if substantiated by a systematic global sampling effort, will necessitate a major reevaluation of ecological and evolutionary theory, as well as conservation strategies and international development policies.
Vertical transmission as the key to the colonization of Madagascar by fungus-growing termites?
by Tania Nobre
co-authored with P Eggleton and DK Aanen
The mutualism between fungus-growing termites (Macrotermitinae) and their mutualistic fungi (Termitomyces) began in... more The mutualism between fungus-growing termites (Macrotermitinae) and their mutualistic fungi (Termitomyces) began in Africa. The fungus-growing termites have secondarily colonized Madagascar and only a subset of the genera found in Africa is found on this isolated island. Successful long-distance colonization may have been severely constrained by the obligate interaction of the termites with fungal symbionts and the need to acquire these symbionts secondarily from the environment for most species (horizontal symbiont transmission). Consistent with this hypothesis, we show that all extant species of fungus-growing termites of Madagascar are the result of a single colonization event of termites belonging to one of the only two groups with vertical symbiont transmission, and we date this event at approximately 13 Mya (Middle/Upper Miocene). Vertical symbiont transmission may therefore have facilitated long-distance dispersal since both partners disperse together. In contrast to their termite hosts, the fungal symbionts have colonized Madagascar multiple times, suggesting that the presence of fungus-growing termites may have facilitated secondary colonizations of the symbiont. Our findings indicate that the absence of the right symbionts in a new environment can prevent long-distance dispersal of symbioses relying on horizontal symbiont acquisition.
45 views
Dispersion and colonisation by fungus-growing termites: vertical transmission of the symbiont helps, but then…?
by Tania Nobre
Article Addendum
Co-authored with DK Aanen
The fungus-growing termites (Macrotermitinae) have developed an obligate mutualistic symbiosis with fungi... more
The fungus-growing termites (Macrotermitinae) have developed an obligate mutualistic symbiosis with fungi (Termitomyces) and, in most cases, the symbiotic partner is collected from the environment upon establishment of a new colony (horizontal transmission). The requirement that partners are able to find and recognize each other after independent reproduction is likely to severely constrain long distance dispersal. In supports of this hypothesis, we have recently shown that a single colonisation of Madagascar by fungus-growing termites has occurred. The successful colonizers belong to the genus Microtermes, known to inherit their symbiont from the parental colony (vertical transmission). However, the fungal symbionts of Madagascar were not monophyletic, as expected under strict vertical transmission. Here we further discuss these findings, and we suggest further bottlenecks to dispersion and propose a transient window for horizontal transmission for the otherwise vertically transmitted Termitomyces strains.

