Gregorio Moreno-Rueda

Area–heterogeneity tradeoff and the diversity of ecological communities

For more than 50 y ecologists have believed that spatial heterogeneity in habitat conditions promotes species richness by increasing opportunities for niche partitioning. However, a recent stochastic model combining the main elements of niche theory and island biogeography theory suggests that environmental heterogeneity has a general unimodal rather than a positive effect on species richness. This result was explained by an inherent tradeoff between environmental heterogeneity and the amount of suitable area available for individual species: for a given area, as heterogeneity increases, the amount of effective area available for individual species decreases, thereby reducing population sizes and increasing the likelihood of stochastic extinctions. Here we provide a comprehensive evaluation of this hypothesis. First we analyze an extensive database of breeding bird distribution in Catalonia and show that patterns of species richness, species abundance, and extinction rates are consistent with the predictions of the area–heterogeneity tradeoff and its proposed mechanisms. We then perform a metaanalysis of heterogeneity–diversity relationships in 54 published datasets and show that empirical data better fit the unimodal pattern predicted by the area–heterogeneity tradeoff than the positive pattern predicted by classic niche theory. Simulations in which species may have variable niche widths along a continuous environmental gradient are consistent with all empirical findings. The area–heterogeneity tradeoff brings a unique perspective to current theories of species diversity and has important implications for biodiversity conservation.

Experimental test of postfire management in pine forests: impact of salvage logging versus partial cutting and nonintervention on bird-species assemblages.

There is an intense debate about the effects of postfire salvage logging versus nonintervention policies on regeneration of forest communities, but scant information from experimental studies is available. We manipulated a burned forest area on a Mediterranean mountain to experimentally analyze the effect of salvage logging on bird-species abundance, diversity, and assemblage composition. We used a randomized block design with three plots of approximately 25 ha each, established along an elevational gradient in a recently burned area in Sierra Nevada Natural and National Park (southeastern Spain). Three replicates of three treatments differing in postfire burned wood management were established per plot: salvage logging, nonintervention, and an intermediate degree of intervention (felling and lopping most of the trees but leaving all the biomass). Starting 1 year after the fire, we used point sampling to monitor bird abundance in each treatment for 2 consecutive years during the breeding and winter seasons (720 censuses total). Postfire burned-wood management altered species assemblages. Salvage logged areas had species typical of open- and early-successional habitats. Bird species that inhabit forests were still present in the unsalvaged treatments even though trees were burned, but were almost absent in salvage-logged areas. Indeed, the main dispersers of mid- and late-successional shrubs and trees, such as thrushes (Turdus spp.) and the European Jay (Garrulus glandarius) were almost restricted to unsalvaged treatments. Salvage logging might thus hamper the natural regeneration of the forest through its impact on assemblages of bird species. Moreover, salvage logging reduced species abundance by 50% and richness by 40%, approximately. The highest diversity at the landscape level (gamma diversity) resulted from a combination of all treatments. Salvage logging may be positive for bird conservation if combined in a mosaic with other, less-aggressive postfire management, but stand-wide management with harvest operations has undesirable conservation effects.

Is there empirical evidence for the cost of begging

Offspring should demand more food than the optimal amount for the parents to bring (parent–offspring conflict), and models on the evolution of parent–offspring communication suggest that an equilibrium is reached when the costs associated with begging make it unprofitable for the offspring to increase its level of begging. Empirical evidence for this cost, however, is mixed, and the conclusions of most of authors are that begging is inexpensive. In this study, the existing empirical evidence for this cost is reviewed. One cost proposed is the attraction of predators due to begging calls, but empirical support for this cost is low. However, studies performed cannot dismiss such a cost. Another possible cost is the metabolic expenditure, but empirical evidence for this cost is mixed, with some works contending that it is low, while others deem it important. Other possible metabolic costs have not been studied. A loss of inclusive fitness may be an important cost for the evolution of begging, and robust empirical evidence does exist for this cost. Costs associated with brood reduction also are reviewed. In conclusion, there is not enough empirical evidence to test the models on the evolution of begging. Most costs proposed have not yet been studied or the approach used has been insufficient to reject the null hypothesis (i.e., absence of cost).

Egg-spot pattern rather than egg colour affects conspecific egg rejection in the house sparrow ( Passer domesticus )

Brood parasitism could be a selective pressure on each female to have a type of egg that permits recognition. House sparrows (Passer domesticus) undergo conspecific brood parasitism and can recognise parasitic eggs. In this study, we analyse the effect of relative size in experimental parasitic eggs compared to the host eggs. We modified egg colour and the spot pattern to determine the influence of these characteristics on egg rejection. Furthermore, we examine whether egg rejection increases with “stimulus summation”. Our results show that egg rejection is not affected by relative egg size. However, changes in the spot pattern proved to exert the highest influence on egg rejection (32.4% of trials), significantly higher than when only egg colour is changed (3.8%). Therefore, our results suggest that parasitism may be a pressure favouring the maintenance of spotted eggs in house sparrow.

Relative influence of habitat heterogeneity, climate, human disturbance, and spatial structure on vertebrate species richness in Spain

Many factors affect the distribution of species richness. This study examines the relative influence of habitat heterogeneity, climate, human disturbance, and spatial structure on the species-richness distribution of terrestrial vertebrates (amphibians, reptiles, birds and mammals) in mainland Spain. The results indicate that spatial structure and environment exert similar influences on species richness. For all four taxa, species richness increases southward and northward, being lower in the center of the country, when controlled for other variables. This may be the result of a peninsular effect, as found in other studies, and reflect the importance of historical events on species richness in the Iberian Peninsula. Climate is more important than habitat heterogeneity in determining species richness. Temperature is positively correlated with amphibian, reptile, and bird species richness, while mammalian species richness is highest at intermediate temperatures. This effect is stronger in ectotherms than among endotherms, perhaps reflecting physiological differences. Precipitation positively correlates with bird and mammalian species richness, but has no effect on ectotherm species richness. Amphibian species richness increases with altitudinal range, and bird species richness with habitat diversity. Human population density is positively correlated with bird and mammalian species richness, but does not affect ectotherm species richness, while amphibian and bird species richness is highest at moderate levels of human land alteration (farmland). However, unexplained variance remains, and we discuss that the effects of environmental variables on species richness may vary geographically, causing different effects to be obscured on a national scale, diminishing the explanatory power of environmental variables.

Age Estimation by a Dental Method: A Comparison of Lamendin’s and Prince & Ubelaker’s Technique

Abstract:u2002 Lamendin et al. (J Forensic Sci 1992;37:1373) developed a general technique to estimate age of adults at death using two dental features: periodontosis and translucency of the tooth root. Prince and Ubelaker (J Forensic Sci 2002;47:107) modified this method, creating a formula for each sex and for different ancestries, and obtained more precise age estimations. In the present study, the validity of each method was tested in 45 males and 34 females of Spanish Caucasian origin, and a novel formula, based on Prince and Ubelaker method, was specifically developed for a population of mixed racial origin (mestizo) from Colombia, and findings obtained were again compared with those yielded by Lamendin adult dental aging technique. The Prince and Ubelaker method proved more accurate than the Lamendin technique in the Spanish Caucasian population, and our Prince and Ubelaker‐based formula was also more accurate than the Lamendin et al. In both populations, the Lamendin method showed a higher mean error in estimations of the age of youngest and oldest individuals. These findings confirm the need to create specific formulas for each human group in order to obtain more accurate age estimates.

Setting conservation priorities for the Moroccan herpetofauna: the utility of regional red lists.

We assess the national conservation status of the amphibians and reptiles of Morocco by applying the IUCN Red List Criteria at the national level and assess its utility as a planning tool to establish regional priorities for conservation. We rely on the accessory data accompanying regional red lists, mainly distribution range and habitats used by, and threats affecting, species of conservation concern. We also correlated some natural history traits to examine the nature and causes of the risk of extinction. With 13 species of amphibians (31% regionally threatened) and 99 species of reptiles (14% regionally threatened), Morocco is one of the Mediterranean countries with the highest diversity of herpetofauna, mainly because of the high percentage of endemism (amphibians 31%, reptiles 24%). The relative frequencies of threatened species were found to be contingent on both taxonomic group and habitat. The overwhelming importance of the threats of small range and number of habitats used by species is different from the threats to the same species at the global level; this demonstrates the usefulness of national or regional analyses of conservation status for setting conservation priorities. The importance of regional assessment derives from the fact that the boundaries set for conservation management are mainly political rather than biogeographical.

Post‐fire salvage logging alters a key plant‐animal interaction for forest regeneration

Post-fire salvage logging is widely implemented worldwide, but there is an increasing concern about its potential impact on the ecosystem. Moreover, there is scant information about the effect of salvage logging on ecosystem processes mediated by species interactions. We manipulated a burnt pine forest to experimentally analyze the effect of burnt-wood management on the colonization of Holm oak (Quercus ilex) mediated by acorn dispersal by Eurasian jays (Garrulus glandarius). Three replicates of three treatments were established in an 18-ha plot: salvage logging (SL), non-intervention (NI), and partial cut plus lopping (PCL; felling and lopping most of the trees but leaving all the biomass in situ). We hypothesized that different burnt-wood management could alter jays landscape perception and thus the pattern of seed dispersal and seedling recruitment. We monitored jay abundance in each treatment for three winters and three breeding periods, and jay flights of potential acorn dispersal between nearby oak trees and the treatments. We also searched for oak seedlings recruited in the experimental plot for five years following the fire. Jays were recorded significantly more times (87%) in NI, and movements to this treatment during the acorn dispersal period were also more frequent (81% of the flights). Oak seedlings were also more abundant in NI (ca. 55%) than in SL or PCL (ca. 25% each), despite a strong effect of small remnants of live pines. The results show that the burnt forest, if unsalvaged, still provides a suitable habitat for jays, while salvage logging reduces the strength of this key plant-animal interaction for oak natural regeneration. Non-intervention policies after a forest fire therefore provide the opportunity for adaptive management that helps reduce restoration costs and increase the resilience of the system.

Oxidative Stress Mediates Physiological Costs of Begging in Magpie (Pica pica) Nestlings

Background Theoretical models predict that a cost is necessary to guarantee honesty in begging displays given by offspring to solicit food from their parents. There is evidence for begging costs in the form of a reduced growth rate and immunocompetence. Moreover, begging implies vigorous physical activity and attentiveness, which should increase metabolism and thus the releasing of pro-oxidant substances. Consequently, we predict that soliciting offspring incur a cost in terms of oxidative stress, and growth rate and immune response (processes that generate pro-oxidants substances) are reduced in order to maintain oxidative balance. Methodology/Principal Findings We test whether magpie (Pica pica) nestlings incur a cost in terms of oxidative stress when experimentally forced to beg intensively, and whether oxidative balance is maintained by reducing growth rate and immune response. Our results show that begging provokes oxidative stress, and that nestlings begging for longer bouts reduce growth and immune response, thereby maintaining their oxidative status. Conclusions/Significance These findings help explaining the physiological link between begging and its associated growth and immunocompetence costs, which seems to be mediated by oxidative stress. Our study is a unique example of the complex relationships between the intensity of a communicative display (begging), oxidative stress, and life-history traits directly linked to viability.

Recent changes in allometric relationships among morphological traits in the dipper (Cinclus cinclus)

Organisms are responding to recent climate warming by changing different aspects of their biology, including morphology. The present work examines the way in which dipper (Cinclus cinclus) morphology has varied over the past 20xa0years (1985–2005) in Sierra Nevada (south-eastern Spain). Tarsus length has decreased, but wing and tail length have increased in the same period. These opposite trends have provoked changes in the allometric relationships among the different parts of the body in the dipper. A decrease in body size is predicted by Bergmann’s rule, and similar results have been found in other birds. However, although this study found a decrease in tarsus length, no change was found for body mass. The increase in wing and tail length may be related to a variation in the trophic niche in response to the decrease in water volume of rivers that occurred during the study period. Other studies show that the dipper’s diet varies with water flow, and water flow has decreased in the study area as a consequence of climatic warming.