Ciencias de la Tierra y Medioambientales
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A melting-pot for Pterodroma petrels on Rapa Nui: ecological divergence and reproductive isolation in a contact zone
(FRONTIERS MEDIA SA, 2023/07/27) Plaza Paula, Cristofari Robin, Gouin Nicolas, Soto-Gamboa Mauricio, Luna-Jorquera Guillermo
Speciation is thought to depend on general ecological segregation rather than on strict allopatry in species with planetary-scale foraging ranges, such as Pterodroma petrels. Separation in both breeding islands and foraging grounds are generally considered to be the conditions for prezygotic isolation. However, it is unclear how both can be maintained in a context of ongoing distributional range shifts due to global change, with range contractions and expansions caused by changing land use in breeding territories and oceanographic conditions impacting productivity areas. In this context, we expect that wherever the fragile balance of allopatric segregation breaks down, gene flow may be re-established across the borders of what is currently considered separated species. In these melting pot areas, fine-scale ecological differentiation is likely the only force opposing panmixia in otherwise highly similar organisms. In this study, we focus on six Polynesian Pterodroma species currently found on Motu Nui, a protected islet offshore of Rapa Nui (Easter Island), four of which have likely extended their breeding range to that island recently. To understand the fine-scale interaction between these closely-related species in their new contact zone, we used an integrative approach combining ecological and genetic methods, including morphometric, bioacoustics, stable isotope niche reconstruction, breeding site characterisation, phenology traits, and both nuclear and mitochondrial DNA markers. We found that significant amounts of gene flow occur across what is currently considered species boundaries, sometimes questioning the relevance of the accepted species classification. Interestingly, our results indicate that multivariate ecological distance between individuals in a group of closely related species (P. alba, P. atrata, P. heraldica, and P. neglecta) is a relevant predictor of gene flow intensity, while more distant species such as P. ultima and P. nigripennis seem to maintain reproductive isolation. Thus, the case of Pterodroma petrels supports the idea that incomplete allopatric speciation processes may be halted or even reversed on a secondary contact zone. Beyond their direct taxonomical relevance, our results underline the importance of considering fine ecological structures for biodiversity mapping and conservation policies.
Diversification trajectories and paleobiogeography of Neogene chondrichthyans from Europe
(CAMBRIDGE UNIV PRESS, 2023/05/01) Villafana Jaime A. A., Rivadeneira Marcelo M. M., Pimiento Catalina, Kriwet Juergen
Despite the rich fossil record of Neogene chondrichthyans (chimaeras, sharks, rays, and skates) from Europe, little is known about the macroevolutionary processes that generated their current diversity and geographical distribution. We compiled 4368 Neogene occurrences comprising 102 genera, 41 families, and 12 orders from four European regions (Atlantic, Mediterranean, North Sea, and Paratethys) and evaluated their diversification trajectories and paleobiogeographic patterns. In all regions analyzed, we found that generic richness increased during the early Miocene, then decreased sharply during the middle Miocene in the Paratethys, and moderately during the late Miocene and Pliocene in the Mediterranean and North Seas. Origination rates display the most significant pulses in the early Miocene in all regions. Extinction rate pulses varied across regions, with the Paratethys displaying the most significant pulses during the late Miocene and the Mediterranean and North Seas during the late Miocene and early Pliocene. Overall, up to 27% and 56% of the European Neogene genera are now globally and regionally extinct, respectively. The observed pulses of origination and extinction in the different regions coincide with warming and cooling events that occurred during the Neogene globally and regionally. Our study reveals complex diversity dynamics of Neogene chondrichthyans from Europe and their distinct biogeographic composition despite the multiple marine passages that connected the different marine regions during this time.
Conservation efforts in need of survey improvement in epigean beetles from the Atacama coast, Chile
(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2023/07/01) Pizarro-Araya Jaime, Villalobos Elizabeth V., Alfaro Fermin M., Moreira-Munoz Andres
The Atacama desert's southern margin includes a poorly explored area of high biotic value with natural areas that are crucial for diversity and conservation. We used pitfall traps to study epigean beetles across 17 sites located along the coast between the Paposo Norte Natural Monument and the Paposo Priority Site. We recorded a total of 3,237 epigean beetles specimens, belonging to 26 families and 97 species. The most well represented families in terms of richness were Curculionidae and Tenebrionidae, and most of the remaining families were represented by fewer than five species. The rarefaction analysis showed that the sampling effort was low, sug-gesting the presence of a hidden and underestimated diversity in the area under study. The ordination analysis showed a clear correlation between elevation and the epigean beetles assemblage, but richness was concentrated in shrubland environments within the Paposo Priority Site and consisted of a large number of rare species (singletons) and species restricted to a few sites of this coastal strip. The high richness estimated for the study area, stress an urgent need to include these units under governmental conservation programs aimed at tackling the multiple threats identified in these fragile arid coastal ecosystems.
Correlation of plasticities to drought and shade: implications for environmental niche overlap in drylands
(WILEY, 2024/03/01) Escobedo Victor M., Rios Rodrigo S., Salgado-Luarte Cristian, Gianoli Ernesto
Phenotypic plasticity can increase the extent of the environmental gradient occupied by a species (niche breadth) and modify the portion of niche space shared among co-occurring species (niche overlap). Thus, phenotypic plasticity may play a role in community assembly processes. Given that plants deal with a multivariate environment, and that functional traits are often correlated, plastic responses to different environmental factors are likely correlated. However, the implications of correlations of plasticities for niche overlap remain unexplored. Here, we present and evaluate a conceptual framework that links correlations of plasticities and niche overlap patterns among co-occurring plant species. We specifically tested in an arid shrubland whether positive, negative, or null correlations between plasticity to light and water availability would be associated with patterns of high, low, or random niche overlap, respectively. Field data identified light and water availability as key factors shaping herbaceous plant community structure. We estimated species' niche breadth and niche overlap using two-dimensional kernel-density estimations (NOK) and standardised effect sizes of Pianka's niche overlap index (OSES). We measured phenotypic plasticity to light and water availability in the six most abundant species in a greenhouse experiment. We used the plasticity index (PI) to test 1) the relationship between plasticity to light and water availability, and 2) the association between overall plasticity (average PI across traits) and niche breadth. We found a positive relationship between plasticity to light and water availability. Increased overall plasticity was associated with a broader niche breadth. Both NOK and OSES estimations indicated a significant niche overlap pattern. Results supported one of the predictions of our conceptual framework: that a positive correlation of plasticities would lead to increased niche overlap. The verified conceptual framework broadens our understanding of the role of phenotypic plasticity in plant community coexistence.
Ancient fires enhance Amazon forest drought resistance
(FRONTIERS MEDIA SA, Maynard Daniel S.) Vedovato Laura B., Carvalho Lidiany C. S., Aragao Luiz E. O. C., Bird Michael, Phillips Oliver L., Alvarez Patricia, Barlow Jos, Bartholomew David C., Berenguer Erika, Castro Wendeson, Ferreira Joice, Franca Filipe M., Malhi Yadvinder, Marimon Beatriz, Marimon Junior Ben Hur, Monteagudo Abel, Oliveira Edmar A., Pereira Luciana O., Pontes-Lopes Aline, Quesada Carlos A., Silva Camila V. J., Espejo Javier Silva E., Silveira Marcos, Feldpausch Ted R.
Drought and fire reduce productivity and increase tree mortality in tropical forests. Fires also produce pyrogenic carbon (PyC), which persists in situ for centuries to millennia, and represents a legacy of past fires, potentially improving soil fertility and water holding capacity and selecting for the survival and recruitment of certain tree life-history (or successional) strategies. We investigated whether PyC is correlated with physicochemical soil properties, wood density, aboveground carbon (AGC) dynamics and forest resistance to severe drought. To achieve our aim, we used an Amazon-wide, long-term plot network, in forests without known recent fires, integrating site-specific measures of forest dynamics, soil properties and a unique soil PyC concentration database. We found that forests with higher concentrations of soil PyC had both higher soil fertility and lower wood density. Soil PyC was not associated with AGC dynamics in non-drought years. However, during extreme drought events (10% driest years), forests with higher concentrations of soil PyC experienced lower reductions in AGC gains (woody growth and recruitment), with this drought-immunizing effect increasing with drought severity. Forests with a legacy of ancient fires are therefore more likely to continue to grow and recruit under increased drought severity. Forests with high soil PyC concentrations (third quartile) had 3.8% greater AGC gains under mean drought, but 33.7% greater under the most extreme drought than forests with low soil PyC concentrations (first quartile), offsetting losses of up to 0.68 Mg C ha(-1)yr(-1) of AGC under extreme drought events. This suggests that ancient fires have legacy effects on current forest dynamics, by altering soil fertility and favoring tree species capable of continued growth and recruitment during droughts. Therefore, mature forest that experienced fires centuries or millennia ago may have greater resistance to current short-term droughts.
Effects of land cover and habitat condition on the bird community along a gradient of agricultural development within an arid watershed of Chile
(ELSEVIER, 2023/10/15) Petit Mariangeles, Celis Cristian, Weideman Craig, Gouin Nicolas, Bertin Angeline
Agricultural activities are a major cause of change in avifauna, frequently resulting in diminished diversity and biotic homogenization, and ultimately compromising ecosystem functioning and resilience. Arid ecosystems, which provide habitat for numerous native and endemic bird species, are vulnerable to global change and valuable in predicting future ecosystem shifts in regions undergoing aridification as a result of climate change. However, the impacts of agriculture on bird communities in arid ecosystems are understudied. Here, we evaluate these impacts in the arid Limari watershed in north-central Chile, a region that has experienced extensive land use conversion to agriculture over the past 50 years. Specifically, we investigated current spatial patterns of avian beta diversity and the impact of landscape context on this diversity facet. Moreover, we evaluated how bird species respond to land cover and habitat conditions and the role of specific bird traits in this regard. To achieve this, we evaluated taxonomic and functional beta diversity across 26 sites distributed along a gradient of agricultural development, applied a beta diversity decomposition procedure, and carried out hierarchical joint species distribution modeling. Our study revealed high taxonomic but low functional beta diversity of the avifauna in the Limari watershed, potentially indicative of past functional homogenization. Contrary to our initial expectations, present agricultural practices did not decrease beta diversity. While human-related landscape elements and agricultural features mostly had neutral or positive effects on bird occurrence, they negatively affected endemic species and certain bird traits related to diet and habitat. Riparian vegetation cover and quality, unrelated to agricultural and urban development, emerged as key factors structuring the regional bird community, and influenced beta diversity. Our results underscore the profound influence of land use change on the avian community in this arid region and the vital role of riparian ecosystems in this regard. Balancing conservation objectives with agricultural development is key to ensuring both the persistence of several functional groups in the region as well as the ecosystem services they provide.
Linnean and Wallacean shortfalls in the knowledge of arthropod species in Chile: Challenges and implications for regional conservation
(ELSEVIER SCI LTD, 2023/05/01) Vergara-Asenjo Gerardo, Alfaro Fermin M., Pizarro-Araya Jaime
Despite global efforts to identify and classify species to improve biodiversity baselines, there still remains large knowledge shortfalls that affect our understanding of the functioning of ecosystems and the design of effective conservation practices. Using the results of the first ongoing large-scale biodiversity inventory for Chile which has already recorded ca. 1,800 species and discovered 87 new species of arthropods, we explore and discuss taxonomy (Linnean) and distribution (Wallacean) shortfalls that preclude large-scale knowledge of arthropod biodiversity for one of the lesser studied groups in the world - the arthropods. Linnean shortfalls are mainly associated with the lack of funding of monitoring and inventory initiatives and the bias towards most charismatic or umbrella species, which in turn trigger effects on the experts' availability, recruitment of taxonomists in research centers, journal impact factors, as well as the availability of scientific collections of type specimens. Instead, Wallacean shortfalls are related to accessibility to remote areas, and the spatial and temporal resolution of sampling efforts. Based on our results and literature review, we discuss the findings and also propose a novel conceptual framework aimed to reduce data gaps and support biodiversity conservation policies, particularly in developing countries. The framework has three main components: (1) the ecosystems, their species, and the threats; (2) the key elements for a biodiversity assessment strategy, and (3) an action plan for protecting biodiversity.
Simulation-based insights into community uniqueness within fragmented landscapes
(SPRINGER, 2023/10/01) Lozada Adriana, Day Casey C., Landguth Erin L., Bertin Angeline
ContextLocal contribution to beta-diversity (LCBD) assesses community composition uniqueness of sites within a region. While it is useful to identify sites with exceptional species composition and, thus, prioritize conservation actions, it is unclear what determines community uniqueness in patchy habitats.ObjectivesThe goal of this study was to clarify the processes underlying community uniqueness in fragmented landscapes and understand how habitat characteristics and community characteristics affect this beta-based diversity indicator.MethodsWe simulated neutral metacommunities and used a variance-based method to assess the contribution of each habitat patch to total beta-diversity, both in terms of replacement and abundance difference. Then, we analyzed the effects of patch and metacommunity characteristics on LCBD.ResultsCommunity uniqueness in species replacement and richness/abundance differences responded differently to community and patch features. Patch quality was the habitat attribute with the strongest effects on all community uniqueness aspects, leading to singular assemblages with high species richness and abundance of rare species. While patch connectivity promoted singular assemblages with high richness, patch size increased community uniqueness in species replacement over time, favoring assemblages with high abundances of rare species.ConclusionsCommunity uniqueness in species replacement and richness/abundance differences convey different information and should be considered separately to propose adequate conservation strategies. Habitat quality emerged as a critical factor in shaping beta-diversity, suggesting that it should be a primary focus of conservation efforts. Future studies are needed to evaluate the generality of our results in different spatial and ecological contexts.
Adaptive plasticity to drought of Grime's CSR strategies
(WILEY, 2023/11/01) Escobedo Victor M., Molina-Montenegro Marco A., Salgado-Luarte Cristian, Stotz Gisela C., Gianoli Ernesto
Grime's strategies (competitor, stress tolerator, ruderal, CSR) represent viable trait combinations with which species deal with environmental conditions. CSR strategies are broadly used to understand plant adaptation to the environment, yet their plastic responses have received little attention. A globally-calibrated tool (StrateFy) estimates CSR strategies using specific leaf area (SLA), leaf dry matter content (LDMC) and leaf area (LA) data, but these three traits can hardly characterise whole-plant responses to the environment individually. CSR strategies reflect tradeoffs among growth, survival and reproduction, at both leaf and whole-plant levels, thus integrating several functions. We hypothesised that CSR strategies and the three constituent traits would show independent plasticity patterns, and that CSR strategies would be more likely to show adaptive responses, i.e. to fit expected functional responses to environmental gradients. We compared phenotypic plasticity to drought in single traits (SLA, LDMC and LA) with the integrated plasticity of the resulting CSR strategy. The study species was the invasive plant Mesembryanthemum crystallinum, which is distributed in arid and semiarid Chile. We found that trait plasticity was rather idiosyncratic and contrary to what would be expected from a functional adjustment to drought: LDMC did not change (expected response: increase) and SLA increased (expected response: decrease). Conversely, plastic responses of CSR strategy and LA were consistent with functionally adaptive responses to drought in all populations: S-strategy increased, while C-strategy and LA decreased. We advocate the use of Grime's CSR theory as an integrative approach to further our understanding of adaptive plasticity in plants.
An exotic plant species indirectly facilitates a secondary exotic plant through increased soil salinity
(SPRINGER, 2023/08/01) de la Cruz Henry J. J., Salgado-Luarte Cristian, Stotz Gisela C. C., Gianoli Ernesto
Indirect facilitation among exotic species may promote their establishment on ecosystems, causing biodiversity losses. However, few experimental studies have identified the mechanisms underlying the indirect facilitation among exotic species. In central-northern Chile, Mesembryanthemum crystallinum (Aizoaceae) is an exotic halophyte that increases soil salinity, while M. nodiflorum is another exotic halophyte -currently less dominant- that often co-occurs with M. crystallinum. In this study, we evaluated the indirect facilitation of M. nodiflorum by M. crystallinum which was mediated by the suppression of salt-susceptible native competitors via increased soil salinity. We further determined the relationship between salt-tolerance traits and the outcome of competitive interactions in saline soil. We included two native Asteraceae plants co-occurring with these Mesembryanthemum species: the -highly probable- salt-susceptible Helenium urmenetae and the salt-tolerant Amblyopappus pusillus. We combined field co-occurrence surveys with greenhouse germination and competition experiments. The Mesembryanthemum species tended to co-occur, which suggests facilitation. Further, the salinity level found under M. crystallinum significantly decreased germination and performance of H. urmenetae, but not of M. nodiflorum and A. pusillus. Accordingly, when in competition, the increased salinity counteracted the negative effect of H. urmenetae on M. nodiflorum biomass, giving M. nodiflorum a competitive advantage. These patterns were associated with decreased specific leaf area and crassulacean acid metabolism expression in M. nodiflorum. In contrast, A. pusillus and M. nodiflorum maintained a neutral interaction regardless of salinity. Overall, our results suggest that M. crystallinum, by increasing soil salinity, may reduce the performance of salt-susceptible competitors, indirectly facilitating the establishment of M. nodiflorum.
No home-field advantage in litter decomposition from the desert to temperate forest
(WILEY, 2023/05/01) van den Brink Liesbeth, Canessa Rafaella, Neidhardt Harald, Knuever Timo, Rios Rodrigo S., Saldana Alfredo, Cavieres Lohengrin A., Oelmann Yvonne, Bader Maaike Y., Tielboerger Katja
1. Litter decomposition rates are determined by the interplay of climate, decomposer organisms and litter quality. It has been suggested that the decomposer community may be locally adapted to litter quality, providing a home-field advantage (HFA) resulting in accelerated decomposition of local compared to non-local litter, after accounting for decomposition differences due to litter quality and the functional capacity of microorganisms. Although widely tested in forests, this hypothesis remains controversial and lacks support of its generality across climates. 2. We therefore tested the HFA hypothesis for litter decomposition in four contrasting ecosystems along an extensive climatic gradient in Chile, using a translocation experiment involving litter from 20 species. In addition to comparing mass loss, we adopted a novel way to disentangle decomposer effects from climate effects, based on loss rates of elements that are actively released from the litter by decomposers during its breakdown versus elements that are simply leached by precipitation. We used the ratios of nitrogen and potassium losses (N/K loss) and phosphorus and potassium losses (P/K loss) to unravel the relative role of microbial breakdown (N and P loss) versus physical leaching (K loss) along the climate gradient. Thus, at each site, we tested whether litter mass loss, N/K loss and P/K loss presented an additional loss due to a HFA for local compared to non-local litter. 3. Across a wide range of environments and litter types, our findings unequivocally contradicted the HFA hypothesis. We observed no significantly positive HFA along the gradient, however, litter quality and the general ability of the decomposer community influenced litter decomposition much more strongly than origin or location of the litter. 4. Our study questions the applicability of the HFA for litter decomposition and calls for more studies that include a large range of climatic conditions to understand the context-dependency of HFA.
Loss of native herbivores triggers diversity decline of ephemeral plant communities
(WILEY, 2023/09/01) Fernandez-Murillo Maria del Pilar, Alfaro Fernando Daniel, Craven Dylan, Gutierrez Julio Roberto, Kelt Douglas A., Meserve Peter L., Troncoso Alejandra J.
Aim: Evaluate the temporal changes in species diversity, composition, and structure of ephemeral plant communities and the seed bank in response to long-term herbivore exclusion over 11 years in plots with and without herbivores.LocationNorth-central Chile.Methods: We obtained information on ephemeral vegetation cover in August and September using the intercept point method and recorded seed abundance in April. The Bosque Fray Jorge National Park Long-Term Socio-Ecological Research (LTSER) provided these records covering 11 years (2009-2019). From the original experiment of 20 plots, we used eight plots divided into two treatments: four plots allowed free access to all herbivores (with herbivores), while the other four plots excluded herbivores (without herbivores).Results: We found that Hill-Shannon diversity increased in plant communities with herbivores and a temporal increase in the cover of the dominant species, Plantago hispidula, under herbivore exclusion. In wet years, species richness and temporal turnover of plant communities increased independently of treatment. Although seed abundance differed among treatments and years, population structure remained constant over time and among treatments, suggesting that the seed bank acts as a buffer against shocks that modify plant community dynamics. Structural equation modeling revealed that precipitation, via its positive effects on Plantago hispidula, increases native plant richness to a greater extent than herbivores. However, in the absence of herbivores, precipitation directly affects native species richness. Moreover, we found that precipitation also influences the native species richness of the seed bank, both directly and indirectly, although its impacts exhibit a time lag.Conclusions: Our study demonstrates that the temporal dynamics of ephemeral plant communities and seed banks in semi-arid ecosystems are strongly coupled to climate variability, highlighting the vulnerability of these communities to biodiversity loss and climate change.
Ecological uniqueness across multiple levels of biodiversity in a Chilean watershed
(SPRINGER, 2024/06/01) Borquez Jessica, Sampertegui Sandra, Wallberg Britt N., Coral-Santacruz Diana, Ruiz Victor H., Samollow Paul B., Gouin Nicolas, Bertin Angeline
To effectively address biodiversity loss, it is essential to prioritize conservation efforts by identifying areas of high conservation value. Ecological uniqueness is a valuable metric for this purpose that decomposes beta diversity into local contributions to beta diversity (LCBD), thereby measuring the contribution of each site within a region to overall biodiversity variation. LCBD has been used extensively to evaluate ecological uniqueness from community composition data, but biodiversity is a multifaceted concept, and community-based ecological uniqueness may not capture the full range of ecological uniqueness occurring at other levels of biological organization. We investigated ecological uniqueness estimates derived from community and species population levels in a watershed of south-central Chile and analyzed their responses to water and habitat quality variables. Ecological uniqueness was estimated at the community level from fish and macroinvertebrate assemblages and at the population level using genetic and morphological data gathered for two invertebrates, the gastropod Chilina dombeiana and the water bug Aquarius chilensis. Our results revealed low spatial congruence between the levels of ecological uniqueness calculated for these different biodiversity components, with mismatches occurring among sites with high LCBD values. Water and habitat quality were major drivers of beta diversity in this watershed, accounting for 43.8% to 74.3% of the spatial variation in LCBDs, and their effects differed among the ecological uniqueness estimates. Overall, our results underscore the idiosyncratic nature of ecological uniqueness metrics, emphasizing the importance of using multiple components of biodiversity to guide conservation actions.
Facilitation by pioneer trees and herbivore exclusion allow regeneration of woody species in the semiarid ecosystem of central Chile
(WILEY, 2023/07/01) Gomez-Fernandez Nicolas A., Smith-Ramirez Cecilia, Delpiano Cristian A., Miranda Alejandro, Vasquez Inao A., Becerra Pablo I.
Questions: Facilitation by pioneer plants and herbivore exclusion may contribute to plant regeneration and restoration of degraded semiarid ecosystems. In this study we evaluated the main and interactive effects of the exclusion of large and medium-sized mammal herbivores and the presence of the pioneer tree Vachellia caven on natural regeneration of woody species in degraded savannas. Location: Two localities of the native sclerophyllous forest of central Chile Methods: Twelve 30 x 40 m exclosures and twelve non-exclosure areas located near native forests were established in savannas of V. caven in each locality. Regeneration coming from seeds and resprouts was sampled both under the canopy of V. caven and without canopy in each exclosure and non-excluded area. Results: After seven years, species richness and density of older regeneration (0.5-2 m high) were positively affected by herbivore exclusion and the presence of V. caven. No significant interaction between herbivore exclusion and V. caven was observed. Younger regeneration (<0.5 m high) was positively affected by herbivore exclusion and the presence of V. caven only in some years with almost no interactive effect. Conclusions: The exclusion of large and medium-sized exotic herbivores and facilitation by pioneer trees are complementary for regeneration. The variable but permanent presence of younger and older regeneration within exclosures and under V. caven during the experiment may lead to an increase of density and diversity of adult plants and recovery of the native forest. However, this process may be slow due to other limiting factors, for instance, reduced precipitation associated with climate change.