Reduced Extinction Rates Research Articles

Conserving tropical biodiversity via strategic spatiotemporal harvest planning

Summary Tropical timber production forests have the potential to harbour many species, but landscape‐level management strategies for minimizing extinctions are lacking. To develop relevant conservation guidelines, we investigated how harvest plans with different spatiotemporal patterns affected the persistence of sessile species with different traits and preharvest characteristics. We confronted this problem via an individual‐based simulation model. We explored several harvest plans with different levels of spatiotemporal aggregation, but equivalent total harvest area, and found that extinction probabilities for each plan varied with species traits and predisturbance characteristics. Most notably, plans with large contiguous harvest units yielded particularly high extinction probabilities for dispersal‐limited habitat specialists with clustered preharvest distributions. Differences between plans were small for some types of species, but highly aggregated plans yielded the highest extinction rates for all extinction‐prone groups. Synthesis and applications. Our simulations suggest that reducing the size of contiguous harvest units, even while total harvest area remains constant, may reduce extinction rates in tropical production forests (assuming that road‐related threats can be effectively managed). Our findings have important implications for tropical conservation efforts and also provide general insight into the compositional effects of disturbances with different spatiotemporal characteristics.

Habitat Availability and Heterogeneity and the Indo-Pacific Warm Pool as Predictors of Marine Species Richness in the Tropical Indo-Pacific

Range overlap patterns were observed in a dataset of 10,446 expert-derived marine species distribution maps, including 8,295 coastal fishes, 1,212 invertebrates (crustaceans and molluscs), 820 reef-building corals, 50 seagrasses, and 69 mangroves. Distributions of tropical Indo-Pacific shore fishes revealed a concentration of species richness in the northern apex and central region of the Coral Triangle epicenter of marine biodiversity. This pattern was supported by distributions of invertebrates and habitat-forming primary producers. Habitat availability, heterogeneity, and sea surface temperatures were highly correlated with species richness across spatial grains ranging from 23,000 to 5,100,000 km2 with and without correction for autocorrelation. The consistent retention of habitat variables in our predictive models supports the area of refuge hypothesis which posits reduced extinction rates in the Coral Triangle. This does not preclude support for a center of origin hypothesis that suggests increased speciation in the region may contribute to species richness. In addition, consistent retention of sea surface temperatures in models suggests that available kinetic energy may also be an important factor in shaping patterns of marine species richness. Kinetic energy may hasten rates of both extinction and speciation. The position of the Indo-Pacific Warm Pool to the east of the Coral Triangle in central Oceania and a pattern of increasing species richness from this region into the central and northern parts of the Coral Triangle suggests peripheral speciation with enhanced survival in the cooler parts of the Coral Triangle that also have highly concentrated available habitat. These results indicate that conservation of habitat availability and heterogeneity is important to reduce extinction of marine species and that changes in sea surface temperatures may influence the evolutionary potential of the region.

Application of MALDI‐MS analysis of Rainforest chemodiversity: a keystone for biodiversity conservation and sustainable use

Brazil hosts the largest proportion of global biodiversity and has demonstrated its commitment in conservation and sustainable use being a key negotiator of the Nagoya Protocol. The “Convention on Biological Diversity” (CBD) calls for actions to reduce extinction rates, something that according with different theories is of fundamental importance for the survival of life on Earth. Contrary to its position in the CBD meetings, Brazil approved a new Forest Code that will result in escalating deforestation, increasing the urgency to demonstrate the value of native species. Extractive-based activities of forest inhabitants are basically economical prospective activities upon the forest richness whose act harmfully against the environment. For centuries, such activity resulted in low profits, triggering a perverse logic that profit increase is necessarily linked to extraction increase. In the last decades, new strategies, as for instance the Sustainable Development Reserve Mamiraua, are showing that forest preservation can also be profitable. Considering the new paradigm of green economy, which now surrounds all this tensioned discussion, we are bringing to the eyesight of policy-makers results on biodiversity conservation research: combining floristic and chemodiversity surveys, using fast high throughput mass spectrometry screening (HT-MSS), to screen forest leaves for economically valued natural products. Matrix-assisted laser desorption/ionization (MALDI) ionizationbased machines are well known by their ability to furnish fast data and can be an important tool for HT-MSS. One of the aims of a long-term ongoing BIOTA/FAPESP research project at the Serra do Mar State Park is to understand ecophysiological traits of leaves, and MALDI-MS was an alternative to identify alkaloids as one of the nitrogen sink. Regarding the following main points: (1) analysis of plant attributed nitrogen fixation and (2) profitable policies for biodiversity conservation, we suggest the screening for alkaloids to be carried out using the leaves of the trees that are top ranked in population density lists within the forest sociology. In order to reach these aims, a set larger than 500 samples was screened for the occurrence of alkaloids and botanical identification. Classical chemical procedures were also applied to validate the results (Dragendorff, Mayer and Wagner assays). In this letter, we provide the first HT MALDI-MS and MALDI-MS/MS forest screening method to provide added value to local specimens of plants. Ionic liquid was used to get around known ionization problems of small molecules (< 1200Da) by avoiding isobaric ions formation by the matrix. Although, LC-ESI-MS is the common technique to screen small molecules, it is highly time consuming, since in six days, only 50 samples can be analyzed. Therefore, our strategy is based on the ability of MALDI to quickly screen a very large number of samples using an ionic liquid as matrix. Using this approach, we can screen up to 200 samples within a 3 h time-frame.

Comment on “Does constructive neutral evolution play an important role in the origin of cellular complexity?” DOI 10.1002/bies.201100010

Speijer [1] has provided a critique of constructive neutral evolution (CNE) and its role in the origin and evolution of cellular complexity [2, 3]. Not surprisingly, we disagree with his assertions. Because his description of the CNE model does not precisely conform to our view of CNE, as we [2, 4] and Stoltzfus [3] have elaborated it, we briefly re-state the model before addressing Speijer’s objections. The underlying premise of CNE is a pre-existing, essentially neutral interaction (RNA:RNA, RNA:protein, protein:protein) between component A, which has some activity, and component B. The activity of A is not dependent on the interaction with B, nor is A’s activity negatively influenced by this interaction. Thus, B could disappear from the scene without any effect on the ‘‘fitness’’ of A. We imagine that a mutation occurs in A that compromises its activity and that normally this mutation would be eliminated from the population by purifying selection. However, the pre-existing interaction with B fortuitously suppresses the effect of this mutation, so that selection pressure is relaxed and themutationmay be harmlessly fixed by drift. Thus, A becomes dependent on B for its activity by virtue of the neutral, ‘‘pre-suppressive’’ effect of the A:B interaction. What we submit does not happen is that the mutation occurs first, after which the interaction with B is positively selected for because it suppresses the deleterious effect of the mutation. Speijer’s ‘‘Think again’’ article [1] embraces several misunderstandings about this important process. First, we note that Speijer’s critique is considerably longer than was our Perspective in Science [3], giving him space to deconstruct several points that hemay consider components or at least entailments of our hypothesis, but that we would not. Let us call these misunderstandings of Type A. Type B misunderstandings reflect Speijer’s conflation of microand macroevolution, or ‘‘levels of selection’’. He fails to recognize that some features that are neutral or even disadvantageous to individuals – and thus not expected to be fixed by selection operating within populations of species – can nevertheless be sufficiently advantageous to species (fostering enhanced speciation or reduced extinction rates) to spread by species or clade selection. Eukaryotic sex might be one of these. Introns could be another. No one really thinks that the insertion of introns was selected for at the level of individuals – that is, that all introns that are currently fixed within a species were fixed because individuals that bore them were at a selective advantage compared to conspecifics that lacked them. Indeed, for individuals within species, intron addition could be slightly deleterious. It might nevertheless still be true that species in which many introns have become fixed do better than species with few introns (speciate more frequently or become extinct less often), because introns facilitate exon shuffling or the elaboration of multiple gene products through alternative splicing. There would thus come to be more intronbearing species (and in consequence more introns) in the world, thanks to species selection. We see many CNEestablished features as evolving like this, influencing however subtly the future evolutionary potential – the ‘‘evolvability’’ – of species, and yet their initial establishment was the consequence of the neutral ratchet we describe. Type C misunderstandings are of a diverse sort. It seems simplest to attempt to correct these as we read DOI 10.1002/bies.201100039

Tree diversity on islands: assembly rules, passive sampling and the theory of island biogeography

AbstractAim Species diversity is distributed heterogeneously through space, for reasons that are poorly understood. We tested three hypotheses to account for spatial variation in coniferous tree species diversity in a temperate island archipelago. The theory of island biogeography (ToIB) predicts that island area affects species diversity both directly (by increasing habitat diversity) and indirectly (by increasing abundances, which in turn reduce extinction rates). The ToIB also predicts that island isolation directly affects species diversity by reducing immigration rates. The passive sampling hypothesis predicts that island area and isolation both affect species diversity indirectly, by increasing and decreasing abundances, respectively. Community assembly rules (i.e. even partitioning of conifer abundances among islands) might also reduce tree species diversity beyond the core predictions of ToIB and the passive sampling hypothesis.Location Barkley Sound, British Columbia, Canada.Methods The abundances of eight coniferous tree species were quantified on 34 islands and two (1 ha) mainland plots. The predictions of the ToIB and the passive sampling hypothesis were tested using path analysis, and null models were used to test for abundance‐based assembly rules and to further test the passive sampling hypothesis.Results Path analysis showed that island area and isolation did not have direct, statistical effects on tree species diversity. Instead, both geographic variables had direct statistical effects on total tree abundances, which in turn predicted tree diversity. Results from several passive sampling null models were correlated with observed patterns in species diversity, but they consistently overestimated the number of tree species inhabiting most islands. A different suite of null models showed support for community assembly rules, or that tree species often reached higher abundances on islands that housed fewer heterospecific trees.Main conclusions Results were inconsistent with the ToIB. Instead, patterns in tree diversity were best explained by a combination of stochastic (passive sampling) and deterministic (assembly rules) processes. Stochastic and deterministic processes are commonly considered to be exclusive explanations for island community structure, but results from this study suggest that they can work synergistically to structure island tree communities.

Global Amphibian Extinction Risk Assessment for the Panzootic Chytrid Fungus

Species are being lost at increasing rates due to anthropogenic effects, leading to the recognition that we are witnessing the onset of a sixth mass extinction. Emerging infectious disease has been shown to increase species loss and any attempts to reduce extinction rates need to squarely confront this challenge. Here, we develop a procedure for identifying amphibian species that are most at risk from the effects of chytridiomycosis by combining spatial analyses of key host life-history variables with the pathogen's predicted distribution. We apply our rule set to the known global diversity of amphibians in order to prioritize pecies that are most at risk of loss from disease emergence. This risk assessment shows where limited conservation funds are best deployed in order to prevent further loss of species by enabling ex situ amphibian salvage operations and focusing any potential disease mitigation projects.

FAAH inhibitor, URB-597, promotes extinction and CB 1 antagonist, SR141716, inhibits extinction of conditioned aversion produced by naloxone-precipitated morphine withdrawal, but not extinction of conditioned preference produced by morphine in rats

Converging evidence suggests that the endogenous cannabinoid (eCB) system is involved in extinction of learned behaviours. Using operant and classical conditioning procedures, the potential of the fatty acid amide (FAAH) inhibitor, URB-597, and the CB 1 antagonist/inverse agonist, SR141716, to promote and inhibit (respectively) extinction of learned responses previously motivated by either rewarding or aversive stimuli was investigated. In the operant conditioning procedure (Expt. 1), rats previously trained to lever press for sucrose reward were administered URB-597 (0.3 mg/kg) or the CB 1 antagonist/inverse agonist SR141716 (2.5 mg/kg) prior to each of three extinction trials. In the conditioned floor preference procedure (Expts 2a–d), rats trained to associate morphine with one of two distinctive floors were administered one of several doses of the CB 1 antagonist/inverse agonist, AM-251 (Expt 2a) or URB-597 (Expt 2b and 2d) prior to each extinction/test trial wherein a choice of both floors was presented and prior to forced exposure to each floor (Expt 2c). In the conditioned floor aversion procedure (Expt. 3), rats trained to associate a naloxone-precipitated morphine withdrawal with a floor cue were administered URB-597 or SR141716 prior to each of 24 extinction/testing trials. URB-597 did not promote and SR141716 did not reduce extinction rates for sucrose reward-induced operant responding (Expt. 1) or morphine-induced conditioned floor preference (Expts. 2a–d). In contrast, URB-597 facilitated, whereas SR141716 impaired, extinction of the conditioned floor aversion (Expt. 3). These data support previous reports that the eCB system selectively facilitates extinction of aversive memories. URB-597 may prove useful in targeting extinction of aversively motivated behaviours.

Historically calibrated predictions of butterfly species' range shift using global change as a pseudo‐experiment

Global changes have the potential to cause a mass extinction. Predicting how species will respond to anticipated changes is a necessary prerequisite to effectively conserving them and reducing extinction rates. Species niche models are widely used for such predictions, but their reliability over long time periods is known to vary. However, climate and land use changes in northern countries provide a pseudo-experiment to test model reliability for predicting future conditions, provided historical data on both species distributions and environmental conditions are available. Using maximum entropy, a prominent modeling technique, we constructed historical models of butterfly species' ranges across Canada and then ran the models forward to present-day to test how well they predicted the current ranges of species. For the majority of species, projections of how we predicted species would respond to known climate changes corresponded with species' observed responses (mean autoregressive R2 = 0.70). This correspondence declined for northerly and very widely distributed species. Our results demonstrate that at least some species are tracking shifting climatic conditions across very large geographic areas and that these shifts can be predicted accurately using niche models. We also found, however, that models for some species fail when projected through time despite high spatial model accuracies during model training, highlighting the need to base management decisions on species assemblages, not individual species.

Demographic analysis of Hubbell's neutral theory of biodiversity

Hubbell's neutral model is increasingly applied in both theoretical and empirical studies but so far little attention has been paid to the ecological mechanisms that determine species diversity in neutral communities. In this contribution we use a stochastic individual-based Markovian model to provide an explicit derivation of Hubbell's local community model from the fundamental processes of reproduction, mortality, and immigration, and show that such derivation provides important insights on the mechanisms regulating species diversity that cannot be obtained from the original model and its previous extensions. One important insight is that the basic parameters of Hubbell's model, community size (J) and the probability that a dying individual will be replaced by an immigrant (m), cannot be considered independent and that their interdependency leads to a counterintuitive trade-off between community size and species diversity. We further demonstrate that Hubbell's treatment of community size as a free parameter hides fundamental mechanisms that influence species diversity through their effect on the size of the community. For example, while in Hubbell's model immigration can only increase species diversity by promoting colonization rates, the demographic derivation shows that immigration can also promote species diversity by reducing extinction rates. Our demographic derivation also unifies previous contrasting predictions about the effect of reproduction on species diversity by showing that both positive and negative effects are possible, and that the balance between the two effects depends on the size of the community. The demographic derivation also reconciles an apparent contradiction between Hubbell's theory and patch occupancy theory, and integrates three previously proposed mechanisms of species diversity, the More Individuals Hypothesis, the rescue effect, and the dilution effect, within a single, unified framework.

Influential factors for natal dispersal in an avian island metapopulation

Dispersal is a key parameter in evolutionary, demographic and conservation theory, but the factors influencing dispersal between populations are rarely known, and the contribution of immigrants to population stability remains uncertain. Using dispersal data from nine island populations of song sparrows, we show that female and male immigrants responded differently to population structure: in females, immigration varied with adult sex ratio; whereas immigration by males was more influenced by population density. These patterns are consistent with the hypothesis that intra‐sexual competition for breeding resources influenced recruitment patterns. Immigrants often constituted a substantial fraction of local population size, and in six cases immigration by females prevented the extirpation of that sex from the island. Breeding vacancies and extirpations may have been more likely in females because their apparent survival was lower than in males. Local recruitment and immigration varied markedly among islands, perhaps as consequence of island size and isolation. Overall, our results suggest that immigration varied with local demography in a sex‐specific way, stabilized population numbers and reduced extinction rates in the smallest populations.

Does species diversity really drive speciation?

It has been hypothesized that total speciation rate may depend on species diversity (Seposky 1978), population sizes (Hubbell 2001), and island area (Losos and Schluter 2000). In a recent paper, Emerson and Kolm (2005) tested the hypothesis that species diversity might promote speciation, by comparing the proportion of endemics in a taxon with the number of species in that taxon, in the Canary Islands and the Hawaiian Islands. They show that the number of species of the taxon is a good predictor of the island endemics in that taxon, and suggest that this result demonstrates the role of species diversity in speciation. We propose an alternative explanation: that the same abiotic variables that control species diversity also influence speciation, and that this phenomenon may render the analysis of Emerson and Kolm circular. Emerson and Kolm performed a stepwise regression of the speciation rate of a taxon, measured as the proportion of endemics of that taxon, against a set of independent variables comprising abiotic factors and the numberofspeciesofthattaxon.However,asweshallsee, if the number of species itself is dependent on the same set of abiotic variables as the speciation rate, then the stepwise regression will select the number of species as the explanatory variable for the speciation rate and lead to the wrong conclusion that the abiotic variables are less important. This statistical artefact happens because the number of species accounts for the compound effect of the abiotic variables. Cadena et al. (2005) point out a particular case of this artefact which happens when both species richness and endemism depend on attributes of islands that influence the average age of resident populations and reduce extinction rates, such as area. Here we show that the statistical artefact can occur more generally for any type of abiotic variable that influences both species richness and speciation or extinction rates.

How is diversity related to species turnover through time?

Empirical studies across a wide range of taxa show that the slopes of species–time relationships often decline as average species richness increases, indicating that more diverse communities have greater temporal stability in species composition. I explored potential explanations for this observation using two simple model formulations for species temporal dynamics. In the Abiotic model, species turnover is governed by the degree of heterogeneity in the environment and the range of species’ tolerances. In this case, more variable conditions lead to lower species richness and higher turnover, but only if the distribution of species’ niche widths and the size of the species pool are independent of the degree of environmental variability. The Biotic model represents direct effects of diversity on turnover through positive or negative feedbacks between diversity and species’ colonization and extinction rates. Declining turnover with increasing richness occurred when higher diversity either facilitated colonization by new species or reduced extinction rates of extant species. Both models could produce the observed pattern of declining turnover at higher diversity under some circumstances, however the conditions for this outcome in the Abiotic model were restrictive and potentially unrealistic. The models provide a process‐based framework for understanding the connection between diversity and species turnover through time.

Community‐based processes behind species richness gradients: contrasting abundance–extinction dynamics and sampling effects in areas of low and high productivity

ABSTRACTAim To consider the role of local colonization and extinction rates in explaining the generation and maintenance of species richness gradients at the regional scale.Location A Mediterranean biome (oak forests, deciduous forests, shrublands, pinewoods, firwoods, alpine heathlands, crops) in Catalonia, Spain.Methods We analysed the relative importance of direct and indirect effects of community size in explaining species richness gradients. Direct sampling effects of community size on species richness are predicted by Hubbell's neutral theory of biodiversity and biogeography. The greater the number of individuals in a locality, the greater the number of species expected by random direct sampling effects. Indirect effects are predicted by the abundance–extinction hypothesis, which states that in more productive sites increased population densities and reduced extinction rates may lead to high species richness. The study system was an altitudinal gradient of forest bird species richness.Results We found significant support for the existence of both direct and indirect effects of community size in species richness. Thus, both the neutral and the abundance–extinction hypotheses were supported for the altitudinal species richness gradient of forest birds in Catalonia. However, these mechanisms seem to drive variation in species richness only in low‐productivity areas; in high‐productivity areas, species richness was uncorrelated with community size and productivity measures.Main conclusions Our results support the existence of a geographical mosaic of community‐based processes behind species richness gradients, with contrasting abundance–extinction dynamics and sampling effects in areas of low and high productivity.

Protected Areas and Prospects for Endangered Species Conservation in Canada

Reserve networks figure prominently in conservation strategies that aim to reduce extinction rates. We tested the effectiveness of the current reserve network at protecting species at risk in Canada, where relatively extensive wilderness areas remain. We compared numbers of terrestrial species at risk included in existing reserves to randomly generated networks with the same total area and number of reserves. Existing reserve networks rarely performed better than randomly selected areas and several included fewer endangered species than expected by chance, particularly in the most biologically imperiled regions. The extent of protected area and density of species at risk were unrelated at either broad (countrywide) or finer spatial scales (50 x 50 km grids), although there was a tendency for the most threatened regions of the country to have few or no protected areas (1.5% of areas with >30 endangered species were in reserves). Although reserves will play a useful role in conserving endangered species that occur within them, reducing extinction rates in a region with much of the world's remaining wilderness will require integrating conservation strategies with agricultural and urban land-use plans outside formally protected areas.

Attacking the act

The Endangered Species Act (ESA), which is 30 years old this year, is no stranger to controversy. As one of the most important pieces of environmental legislation ever introduced in the US, it has been a battleground of conflicting interests almost since its inception. This year will be no different. Dr Sue Silver, Editor-in-Chief The aim of the ESA is to preserve the biological heritage of the US by protecting species in danger of extinction. To achieve this, it is also necessary to conserve the habitat in which the species is found, and to devise recovery plans to help restore viable population levels. When the act passed into law, President Nixon said, “Nothing is more priceless and more worthy of preservation than the rich array of animal life with which our country has been blessed”. Unfortunately, few people seem to have heard the muttered response, “Unless it happens to live on my land, or get in the way of my development plans”. Even supporters of the ESA recognize that it is by no means perfect. Getting a species listed as “protected” is a long, slow process, and because species are not included until they are in serious trouble, protected status often does not prevent them from disappearing. There are currently 986 species listed as endangered, with 276 more classed as threatened. Since 1973, only about 30 species have been removed from the list, and in seven cases this was because they became extinct (http://endangered.fws.gov). Furthermore, as Frontiers legal columnist Douglass Rohrman explains (p 107), the act has always been hampered by a lack of resources. However, the ESA's greatest weakness, according to some, is that it offers no incentive to private landowners to protect endangered species on their land, while at the same time preventing them from developing that land as they wish. There have been a number of attempts to “improve” the ESA, each calling for the same things – more consultations, more layers of bureaucracy, and more data collection before decisions are made. These demands for more data will simply result in species declining, often to the point of no return, while we study them. Now the ESA is about to come under renewed attack. Richard Pombo (R-CA), author of two previous bills to overhaul the ESA, has become Chair of the House Resources Committee. Pombo is a staunch supporter of private property rights and consequently is not a fan of the ESA, so these two subjects are likely to be at the top of his agenda. Pombo contends that, as a result of current ESA regulations, owners often destroy endangered species (or their habitat) for fear of losing control of their property. He wants to introduce a compensation package for landowners, to encourage them to host protected species, but also to lift restrictions on land use and destruction of habitat. However, since there is currently no evidence that the necessary funds exist to provide this compensation, landowners will gain while endangered species lose out. The scientific community, and even the lay public, recognize that the current rate of species extinctions, and the consequent loss of biodiversity, will have severe repercussions – if not for the current generation, then definitely for future ones. Whether one sees species extinctions purely in terms of lost ecosystem services, or from the moral perspective that we have a duty of care towards the living heritage we share the planet with, the end result is the same. Each attempt to improve the act forces scientists to argue against plans to further complicate and slow the listing process. If we truly wish to reduce extinction rates, changes to the legislation should aim to simplify procedures, speed up the listing process, and provide funding for the research necessary to begin turning the situation around. Perhaps in this particular instance Richard Pombo has a point. If funds could be made available to offer private landowners sufficient incentives to preserve endangered species on their property, then their elected representatives might find it easier to commit the necessary resources and design a more effective, proactive ESA.

Patterns of endemic extinctions among island bird species

The relationship between island biogeography and the vulnerability of island biota to extinction as a result of human activities was examined. In particular, this study analyzed whether island area, maximum elevation of an island, isolation from the nearest continental landmass, or date of human colonization had statistically significant relationships with the proportion of endemic island bird species that have become endangered or extinct. The study examined islands or island groups with endemic bird species, and which have never been connected to a continental landmass. Both modern and fossil bird species were incorporated into the analysis. Islands that were colonized by humans earliest had the lowest proportion of modern species alone, and modern and fossil species combined, that have gone extinct. However, date of human arrival was not correlated with the proportion of modern species that are endangered. Maximum elevation of an island was negatively correlated with the proportion of modern species that are extinct, and was positively correlated with the proportion of modern species that are endangered. Area was negatively correlated with the proportion of modern species that are endangered. Isolation of islands was not significantly correlated with the proportion of modern species extinct or endangered, but was positively correlated with the proportion of modern and fossil species combined that have gone extinct. These results indicate that the initial spasm of island bird extinctions due to human contact may have, in part, passed. They also indicate that bird species on islands colonized earliest by humans may have had more time to adapt to the presence of man and his commensal species, resulting in reduced extinction rates.

High Species Diversity in Fleshy‐Fruited Tropical Understory Plants

Key innovations may increase the number of taxa in a clade that possesses the proposed innovation in comparison to its sister group that lacks the trait through either increased speciation or reduced extinction rates. Comparing sister clades across several independent lineages provides statistical support that the trait has increased species diversity. Previous studies have indicated that there may not be a relationship between biotic dispersal and higher species diversity, but only a few of these studies specified habit, habitat, or type of disperser. No previous study has specified all of the above parameters and used a phylogenetic approach. This article examines species diversity in numerous lineages of tropical understory plants with small, fleshy, bird-dispersed fruits for which a reliable estimate of phylogenetic relationships is available. Clades with fleshy fruits are significantly more diverse than sister clades with dry fruits.

High Species Diversity in Fleshy-Fruited Tropical Understory Plants

Key innovations may increase the number of taxa in a clade that possesses the proposed innovation in comparison to its sister group that lacks the trait through either increased speciation or reduced extinction rates. Comparing sister clades across several independent lineages provides statistical support that the trait has increased species diversity. Previous studies have indicated that there may not be a relationship between biotic dispersal and higher species diversity, but only a few of these studies specified habit, habitat, or type of disperser. No previous study has specified all of the above parameters and used a phylogenetic approach. This article examines species diversity in numerous lineages of tropical understory plants with small, fleshy, bird‐dispersed fruits for which a reliable estimate of phylogenetic relationships is available. Clades with fleshy fruits are significantly more diverse than sister clades with dry fruits.

Urban biogeography : City parks as islands for Diptera and Coleoptera.

Species richness and abundance of Diptera and Coleoptera were assessed in nine city parks in Cincinnati, Ohio, USA. Species richness for each park was related to the area of the park in a manner predicted by island biogeography theory. The z values for the Diptera and Coleoptera were 0.235 and 0.222 respectively. These values are somewhat higher than expected for continental islands and suggest that the Diptera and Coleoptera in these parks are as isolated as many species which occur on true oceanic islands.A stepwise multiple regression was conducted, regressing species richness against several aspects of habitat diversity in the parks. It was found that area alone was the best predictor of species richness. This result, coupled with data on population sizes, suggests that increased area acts primarily to reduce extinction rates rather than to provide new habitats for specialized species.

Turnover Rates in Insular Biogeography: Effect of Immigration on Extinction

Demographic and genetic contributions from conspecific immigrants tend to reduce extinction rates of insular populations. The MacArthur—Wilson model of island biogeography is modified to provide for this effect of immigration on extinction, which we call the rescue effect. This new model predicts that when immigration rates are high relative to extinction rates, turnover rate is directly related to the distance between an island and the source of colonizing species. A field study of the distribution of arthropods among isolated plants supports the model.