Paola Laiolo

Landscape bioacoustics allow detection of the effects of habitat patchiness on population structure

Landscape structure may affect individual dispersal abilities, thus influencing the genotypic and phenotypic composition of populations. We analyzed the interplay among landscape, behavior, and evolutionary processes by correlating habitat patchiness to the variability in vocalizations of Duponts Lark Chersophilus duponti, one of the most habitat-selective and rare European songbirds. We tape-recorded males throughout the species distribution in Spain, analyzed the spatial patterns of territorial call variation at different scales (individuals, populations, and broad geographic areas), and related acoustic variability to patterns of isolation by geographic distance and by landscape unsuitability (calculated by building a predictive model of habitat suitability). The differentiation of spectro-temporal call features resulted from both isolation by distance and isolation by landscape unsuitability mechanisms. Landscape connectivity was often a better determinant of call differentiation than simple straight-line distance between individuals, providing the first evidence that call transmission can be limited by the presence and distribution of patches of adequate habitat, which likely mediates bird dispersal. Landscape patchiness resulted in a reduction of acoustic diversity (repertoire size) within populations, and a parallel increase in differentiation among populations. Landscape bioacoustics can represent a promising tool for estimating population structure, although the study of animal communication cannot be viewed as an alternative, but a source of complementary information to genetics, given that it provides evidence of male-male transmission and social and cultural phenomena that are currently undetectable from molecular data.

Erosion of animal cultures in fragmented landscapes

In the study of fragmented populations, genetic diversity has received a good deal of attention, whereas traits that are not genetically inherited have been generally overlooked. We analyzed variation in cultural traditions (song and call repertoire) of a small songbird, Duponts lark (Chersophilus duponti), with respect to landscape and demographic parameters associated with anthropogenic habitat fragmentation. As patch size, male population, and mean dispersal distance decrease, individual and population song repertoires pass through a cultural bottleneck and significantly decline in variety. Similarly, isolation is associated with impoverishment of population call pools. That declining populations face problems of cultural erosion, possibly anticipating extinction, suggests cultural diversity should be taken into account when dealing with the conservation of species in which social learning is important. Cultural elements could be viewed as a novel, fourth level of biodiversity that may complement the ...

Distress calls may honestly signal bird quality to predators

In predator–prey interactions, both interactors may benefit from sharing information about prey vulnerability. We examined the relationship between calls used to discourage close predators (distress calls) and the health condition of the caller to test whether these signals are reliable indicators of prey quality. The structure of calls from captured lesser short–toed larks Calandrella rufescens was related to their body condition and T–cell–mediated immunocompetence. Birds in better nutritional and immunological condition utter harsher calls (i.e. they spread the call energy over a wider range of frequency) than birds in poorer conditions. Hence, the harshness of distress calls seems honestly to signal the health status of prey and thus their ability to escape, on which the predator might base its optimal foraging choice. Previous studies have investigated the honesty of songs that have evolved via sexual selection, but this is the first study, to our knowledge, the demonstrates a relationship between individual quality and a vocalization primarily shaped by natural selection.

Fate of unproductive and unattractive habitats: recent changes in Iberian steppes and their effects on endangered avifauna

SUMMARY Steppe ecosystems worldwide are affected by agricultural development and generally unprotected. Spanish shrub-steppes contain endangered avifauna, and this paper analyses their state of habitat conservation, the changes that have occurred in the last decade, primary productivity and its relationship with land exploitation and the richness of threatened birds, and avifauna responses to habitat loss. Fifty steppe remnants distributed throughout Spain and inhabited by Dupont’s lark Chersophilus duponti, an endangered passerine representative of shrub steppe-like habitat, were studied. The study fragments were generally affected by agriculture exploitation, and steppe cover had significantly decreased in several isolated patches during the period 1991‐1999. Steppe habitat recovered slightly in areas with low plant productivity indices, and decreased in extent in the most productive areas, in line with EU (European Union) agricultural policy recommendations to abandon marginal land of low productivity. The low overall primary productivity of Iberian steppes opened the way to industrial activities (mining, waste collection and wind-farming), which in the study areas occurred more frequently in steppe than in other habitat types that are more attractive to the public (woodland) or more productive (farmland). The emerging wind industry little affected the study plots, but the presence of anemometers suggests that the impact is likely to increase in the near future, especially in the largest steppelands. Dupont’s lark was sensitive to the fragmentation of its habitat; crowding occurred in isolated and small fragments, possibly as a consequence of habitat constraints and species dispersal dynamics. Fragments inhabited by Dupont’s lark also hosted other steppe birds with a high conservation value; the community of endangered birds, mostly adapted to arid conditions, was richest in the less productive sites. Only four shrub-steppe fragments are given some kind of protection throughout Spain, testifying to the limited public awareness about the value of this habitat. Urgent action is required to restore this habitat through abandonment of less productive farmland, and to create a network of protected and connected steppelands, in order to assure the long-term viability of steppe specialists and the preservation of a habitat that is unique in Western Europe. This should be coupled to an effort to increase social consciousness of the ecological value of steppes and arid landscapes in general.

Diversity and structure of the bird community overwintering in the Himalayan subalpine zone: is conservation compatible with tourism?

Abstract In this paper data on the bird community overwintering in the subalpine zone of Sagarmatha National Park (Khumbu Himal area, Nepal) are presented, with particular emphasis on habitat structure and bird–habitat relationships. The impact of land use and management on the conservation of diversity is analysed and discussed. Four habitat types were considered: mixed forest, pure juniper forest, dwarf rhododendron shrubbery and cultivations. Mixed forest supports the richest avifauna, but forest birds are sensitive to over-exploitation of their habitat: bird density, species richness and diversity are significantly lower in heavily utilised forest. Here, the lower density of rhododendrons, firs and birches, together with their younger age, seem to be unattractive to insectivorous gleaners and granivores, which prefer tree- and understorey-rich spots of unutilised forest. Terraced cultivations also are a rich habitat for wintering birds, and traditional cultivations with hedgerows and scattered bushes have a great potential for bird conservation. Juniper woods are important habitats mainly for frugivores, whereas dwarf rhododendron shrubberies support the poorest avifauna. This study emphasises that forest birds and habitats are severely threatened. As deforestation is the consequence of the tourist pressure for fuelwood along the trekking route to Mt. Everest Base Camp, a strict regulation of tourist-related developments is essential to preserve biodiversity and manage land uses within sustainability.

Climate Change and Eco-Evolutionary Dynamics in Food Webs

Abstract The analysis of the causes of selection is in essence a problem in ecology Wade and Kalisz 1990 Past evolution determines the genetically determined available phenotypes in populations which affect ecological dynamics in communities, shaping in turn the selective pressures that further model phenotypes. Because an increase in temperature increases metabolic rates and encounter rates, climate change may have profound eco-evolutionary effects, possibly affecting the future persistence and functioning of food webs. We introduce a semi-spatially explicit individual-based model (IBM) framework to study functional eco-evolutionary dynamics in food webs. Each species embedded in the web includes 13 genetically determined and multidimensionally variable traits (the G matrix), 4 of which are flexible physiological and behavioural (personality) traits that respond to temperature. An increase in temperature and stronger correlation among traits leads to stronger trophic cascades but higher stochasticity, with higher probability of extinction for some trophic levels. A combination of the abiotic (temperature) and biotic (predators’ presence/absence) matrix of selective agents (the O matrix) generates differential selection for activation energies for metabolic rates and several instances of correlational selection (selection in one trait changes with the levels of another), suggesting how global warming might favour certain trait combinations. Our results and the future prospects of this IBM approach open new avenues for climate change research.

Local climate determines intra- and interspecific variation in sexual size dimorphism in mountain grasshopper communities

The climate is often evoked to explain broad‐scale clines of body size, yet its involvement in the processes that generate size inequality in the two sexes (sexual size dimorphism) remains elusive. Here, we analyse climatic clines of sexual size dimorphism along a wide elevation gradient (i) among grasshopper species in a phylogenetically controlled scenario and (ii) within species differing in distribution and cold tolerance, to highlight patterns generated at different time scales, mainly evolutionary (among species or higher taxa) and ontogenetic or microevolutionary (within species). At the interspecific level, grasshoppers were slightly smaller and less dimorphic at high elevations. These clines were associated with gradients of precipitation and sun exposure, which are likely indicators of other factors that directly exert selective pressures, such as resource availability and conditions for effective thermoregulation. Within species, we found a positive effect of temperature and a negative effect of elevation on body size, especially on condition‐dependent measures of body size (total body length rather than hind femur length) and in species inhabiting the highest elevations. In spite of a certain degree of species‐specific variation, females tended to adjust their body size more often than males, suggesting that body size in females can evolve faster among species and can be more plastic or dependent on nutritional conditions within species living in adverse climates. Natural selection on female body size may therefore prevail over sexual selection on male body size in alpine environments, and abiotic factors may trigger consistent phenotypic patterns across taxonomic scales.

Characterizing the spatial structure of songbird cultures.

Recent advances have shown that human-driven habitat transformations can affect the cultural attributes of animal populations in addition to their genetic integrity and dynamics. Here I propose using the song of oscine birds for identifying the cultural spatial structure of bird populations and highlighting critical thresholds associated with habitat fragmentation. I studied song variation over a wide geographical scale in a small and endangered passerine, the Duponts Lark Chersophilus duponti, focusing on (1) cultural population structure, to determine a statistical representation of spatial variation in song and identify cultural units, and (2) the minimum patch size needed for an individual to develop a stable repertoire. I found that overall song diversity depends on variation among populations (beta-cultural diversity). Abrupt thresholds occurred in the relationships between individual song dissimilarity and geographic distance, and between individual song diversity and patch area. Spatial autocorrelation analysis showed that populations located as little as 5 km apart may have independently evolved their song traditions. Song diversity stabilized in patches as small as 100 ha supporting as few as 8-20 males. Song repertoires of smaller patches were significantly poorer. Almost one-quarter of the study populations inhabited patches <100 ha, and their cultural traditions appear to have eroded. The analysis of spatial patterns in birdsong may be a useful tool for detecting subpopulations prone to extinction.

Climate-driven variation in the intensity of a host-symbiont animal interaction along a broad elevation gradient.

Gradients of environmental stress may affect biotic interactions in unpredictable ways responding to climate variation, depending on the abiotic stress tolerance of interacting partners. Here, we study the effect of local climate on the intensity of feather mites in six mountain passerines along a 1400 m elevational gradient characterized by shifting temperature and rainfall. Although obligatory symbionts of warm-blooded organisms are assumed to live in mild and homeothermic environments, those inhabiting external, non-blood-irrigated body portions of the host organism, such as feather mites, are expected to endure exposure to the direct influence of a fluctuating climate. As expected, feather mite intensity declined with elevation in all bird species, a pattern that was also found in cold-adapted passerines that have typical alpine habits. The elevation cline was mainly explained by a positive effect of the average temperature upon mite intensity in five of the six species studied. Precipitation explained less variance in mite intensity than average temperature, and showed a negative correlation in half of the studied species. We found no climate-driven migration of mites along the wings of birds, no replacement of mite species along elevation gradients and no association with available food resources for mites (estimated by the size of the uropygial gland). This study suggests that ectosymbionts of warm-blooded animals may be highly sensitive to climatic variation and become less abundant under stressful environmental conditions, providing empirical evidence of the decline of specialized biotic interactions among animal species at high elevations.

Predation of experimental nests is linked to local population dynamics in a fragmented bird population

Artificial nest experiments (ANEs) are widely used to obtain proxies of natural nest predation for testing a variety of hypotheses, from those dealing with variation in life-history strategies to those assessing the effects of habitat fragmentation on the persistence of bird populations. However, their applicability to real-world scenarios has been criticized owing to the many potential biases in comparing predation rates of artificial and natural nests. Here, we aimed to test the validity of estimates of ANEs using a novel approach. We related predation rates on artificial nests to population viability analyses in a songbird metapopulation as a way of predicting the real impact of predation events on the local populations studied. Predation intensity on artificial nests was negatively related to the species annual population growth rate in small local populations, whereas the viability of large local populations did not seem to be influenced, even by high nest predation rates. The potential of extrapolation from ANEs to real-world scenarios is discussed, as these results suggest that artificial nest predation estimates may predict demographic processes in small structured populations.