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opencc-zeroDec 2014View details →

Data from: Age-related mortality explains life history strategies of tropical and temperate songbirds

Life history theory attempts to explain why species differ in offspring number and quality, growth rate, and parental effort. I show that unappreciated interactions of these traits in response to age-related mortality risk challenge traditional perspectives and explain life history evolution in songbirds. Counter to a long-standing paradigm, tropical songbirds grow at similar overall rates to temperate species but grow wings relatively faster. These growth tactics are favored by predation risk, both in and after leaving the nest, and are facilitated by greater provisioning of individual offspring by parents. Increased provisioning of individual offspring depends on partitioning effort among fewer young because of constraints on effort from adult and nest mortality. These growth and provisioning responses to mortality risk finally explain the conundrum of small clutch sizes of tropical birds.

opencc-zeroDec 2017View details →

Data from: Applying generalised allometric regressions to predict live body mass of tropical and temperate arthropods

1. The ecological implications of body size extend from the biology of individual organisms to ecosystem–level processes. Measuring body mass for high numbers of invertebrates can be logistically challenging, making length-mass regressions useful for predicting body mass with minimal effort. However, standardised sets of scaling relationships covering a large range in body length, taxonomic groups, and multiple geographical regions are scarce. 2. We collected 6212 arthropods from 19 higher-level taxa in both temperate and tropical locations to compile a comprehensive set of linear models relating live body mass to a range of predictor variables. We measured live weight (hereafter, body mass), body length and width of each individual and conducted linear regressions to predict body mass using body length, body width, taxonomic group and geographic region. Additionally, we quantified prediction discrepancy when using parameters from arthropods of a different geographic region. 3. Incorporating body width into taxon- and region-specific length-mass regressions yielded the highest prediction accuracy for body mass. Using regression parameters from a different geographic region increased prediction discrepancy, causing over- or underestimation of body mass depending on geographical origin and whether body width was included. 4. We present a comprehensive range of parameters for predicting arthropod body mass and provide guidance for selecting optimal scaling relationships. Given the importance of body mass for functional invertebrate ecology and the paucity of adequate regressions to predict arthropod body mass from different geographical regions, our study provides a long-needed resource for quantifying live body mass in invertebrate ecology research.

opencc-zeroDec 2017View details →

Data from: Reproductive behaviour indicates specificity in resource use: phylogenetic examples from temperate and tropical insects

Specificity (= the degree of ecological specialisation) is one of the fundamental concepts of the science of ecology. Ambiguities on how to define and measure specificity have however complicated respective research efforts. Here we propose that, in insects, a behavioural trait –adult oviposition latency in captivity without a favourable host plant – correlates with a species' specificity in larval host use. In the absence of a suitable host, monophagous insects are expected to wait for a long time before commencing oviposition, with the long waiting time corresponding to careful host location behaviour in nature. Polyphagous insects, in contrast, should be selected for an increased oviposition rate at the expense of the quality of oviposition substrate encountered and will on average have a short latency time. Using experimentally derived data on oviposition latency, we performed a phylogenetically informed analysis based on Bayesian inference to show that this variable correlates with host specificity (larval diet breadth) in a sample of North-European species of geometrid moths. A closely related index – the probability to lay any eggs on an unfavourable substrate – shows an analogous pattern. To provide an example of how these indices can be applied, we compare our sample of geometrid moths from Northern Europe with a sample from equatorial Africa. A comparative analysis based on an original phylogenetic reconstruction found no differences between the two study sites in parameters of oviposition behaviour. We conclude that behavioural tests can provide information about ecological interactions when the latter cannot be directly recorded. Our example study also hints at the possibility that host specificity of herbivores is not necessarily higher in a tropical region compared to a temperate one.

opencc-zeroDec 2013View details →

Data from: Reciprocal specialization in multihost malaria parasite communities of birds: a temperate-tropical comparison

How specialization of consumers with respect to resources varies with respect to latitude is poorly understood. Coexistence of many species in the tropics might be possible only if specialization also increases. Alternatively, lower average abundance of more diverse biotic resources in the tropics might force consumers to become more generalized foragers. We examine levels of reciprocal specialization in an antagonistic system—avian malaria—to determine whether the number of host species used and/or parasite lineages harbored differ between a temperate and a tropical assemblage. We evaluate the results of network analysis, which can incorporate both bird and parasite perspectives on specialization in one quantitative index, in comparison to null models. Specialization was significantly greater in both sample sites than predicted from null models. We found evidence for lower per-host species parasite diversity in temperate compared to tropical birds. However, specialization did not differ between the tropical and temperate sites from the parasite perspective. We supplemented the network analysis with estimates of specialization that incorporate phylogenetic relationships of associates and found no differences between sites. Thus, our analyses indicate that specialization within an antagonistic host-parasite (resource-consumer) system varies little between tropical and temperate localities.

opencc-zeroDec 2016View details →

Data from: Are the radiations of temperate lineages in tropical alpine ecosystems pre-adapted?

Aim: Tropical mountains around the world harbour an extraordinarily rich pool of plant species and are hotspots of biodiversity. Climatically, they can be zoned into montane climates at mid-altitudes and tropical alpine climates above the tree line. Around half of the tropical alpine species belong to plant lineages with a temperate ancestry, although these regions are often geographically distant. We test the hypothesis that these temperate lineages are pre-adapted to the tropical alpine climate. Location: New World, with a focus on tropical alpine Andes. Time period: Miocene to present. Major taxa studied: Flowering plants. Methods: We build multidimensional environmental models representing the full space of New World climates. We quantify the environmental similarity between the tropical alpine ecosystem and those of potential source areas, while correcting for regional differences by kernel density smoothers. Based on spatial observations of the genus Hypericum (St John's Wort), we quantify niche overlap and test for niche conservatism following intercontinental dispersal using density-weighted nonparametric tests. A dated species tree, biogeographical estimation, multi-optima Ornstein–Uhlenbeck models and model selection approaches are used to test for niche shifts during establishment in the tropical alpine Andes. Results: The tropical alpine ecosystem is isolated by its climate from adjacent regions and is climatically similar to temperate lowland biomes of both hemispheres. Niche conservatism is evident in the study group, except in the tropical alpine lineage that is characterized by niche expansion and shifts in temperature optima. Main conclusions: Our results reject the pre-adaptation hypothesis and instead suggest pronounced niche evolution during colonization of tropical alpine ecosystems. Establishment involved substantial niche shifts, mainly in temperature-related variables, and resulted in a tremendous proliferation of species in the newly invaded tropical alpine ecosystem.

opencc-zeroDec 2014View details →

Data from: Temperate radiations and dying embers of a tropical past: the diversification of Viburnum

We used a near-complete phylogeny for the angiosperm clade Viburnum to assess lineage diversification rates, and to examine possible morphological and ecological factors driving radiations. Maximum-likelihood and Bayesian approaches identified shifts in diversification rate and possible links to character evolution. We inferred the ancestral environment for Viburnum and changes in diversification dynamics associated with subsequent biome shifts. Viburnum probably diversified in tropical forests of Southeast Asia in the Eocene, with three subsequent radiations in temperate clades during the Miocene. Four traits (purple fruits, extrafloral nectaries, bud scales and toothed leaves) were statistically associated with higher rates of diversification. However, we argue that these traits are unlikely to be driving diversification directly. Instead, two radiations were associated with the occupation of mountainous regions and a third with repeated shifts between colder and warmer temperate forests. Early-branching depauperate lineages imply that the rare lowland tropical species are 'dying embers' of once more diverse lineages; net diversification rates in Viburnum likely decreased in these tropical environments after the Oligocene. We suggest that 'taxon pulse' dynamics might characterize other temperate plant lineages.

opencc-zeroOct 2019View details →

Multiple metrics of latitudinal patterns in insect pollination and herbivory for a tropical-temperate congener pair

The biotic interactions hypothesis posits that biotic interactions are more important drivers of adaptation closer to the equator, evidenced by "stronger" contemporary interactions (e.g. greater interaction rates) and/or patterns of trait evolution consistent with a history of stronger interactions. Support for the hypothesis is mixed, but few studies span tropical and temperate regions while experimentally controlling for evolutionary history. Here, we integrate field observations and common garden experiments to quantify the relative importance of pollination and herbivory in a pair of tropical-temperate congeneric perennial herbs. Phytolacca rivinoides and P. americana are pioneer species native to the Neotropics and the eastern USA, respectively. We compared plant-pollinator and plant-herbivore interactions between three tropical populations of P. rivinoides from Costa Rica and three temperate populations of P. americana from its northern range edge in Michigan and Ohio. For some metrics of interaction importance, we also included three subtropical populations of P. americana from its southern range edge in Florida. This approach confounds species and region but allows us, uniquely, to measure complementary proxies of interaction importance across a tropical-temperate range in one system. To test the prediction that lower-latitude plants are more reliant on insect pollinators, we quantified floral display and reward, insect visitation rates, and self-pollination ability (autogamy). To test the prediction that lower-latitude plants experience more herbivore pressure, we quantified herbivory rates, herbivore abundance, and leaf palatability. We found evidence supporting the biotic interactions hypothesis for most comparisons between P. rivinoides and north-temperate P. americana (floral display, insect visitation, autogamy, herbivory, herbivore abundance, and young-leaf palatability). Results for subtropical P. americana populations, however, were typically not intermediate between P. rivinoides and north-temperate P. americana, as would be predicted by a linear latitudinal gradient in interaction importance. Subtropical young-leaf palatability was intermediate, but subtropical mature leaves were the least palatable, and pollination-related traits did not differ between temperate and subtropical regions. These nonlinear patterns of interaction importance suggest future work to relate interaction importance to climatic or biotic thresholds. In sum, we found that the biotic interactions hypothesis was more consistently supported at the larger spatial scale of our study.

opencc-zeroNov 2019View details →

Data from: Primary dermal fibroblasts and pectoralis muscle show similar patterns of oxidative stress in tropical and temperate birds despite differing life-histories

Tropical birds have a "slower pace of life," with lower rates of whole-animal metabolism, smaller metabolically active organs, and lower cellular metabolic rates than their temperate counterparts. Oxidative stress is a physiological mechanism that may dictate differing life-histories such as those found between tropical and temperate birds. Oxygen is required to make ATP, resulting in the production of reactive oxygen species (ROS). If left unchecked, ROS can structurally alter proteins, induce mutations in DNA, and damage structural lipids. To combat accumulating oxidative damage, organisms have evolved an elaborate and costly antioxidant system that serves to sequester ROS before they wreak cellular havoc. We examined whether oxidative stress would differ between tropical and temperate birds. We used isolated primary dermal fibroblasts and pectoralis muscle tissue for measurements. We measured four aspects of oxidative stress in primary fibroblasts – reduced glutathione (GSH) concentration, ROS production, mitochondrial content, and lipid peroxidation (LPO) damage. We found no significant differences in the four variables between temperate and tropical birds.. In muscle tissue, we measured catalase (CAT), superoxide dismutase (SOD) glutathione peroxidase (GPx) activity, peroxyl and hydroxyl scavenging capacity, and LPO damage. We found that peroxyl scavenging capacity was significantly higher in tropical birds compared with temperate birds.

FIGURE 13 in Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico

FIGURE 13. Colanthura guerreronegroensis sp. nov., holotype, female, 8.7 mm, CIB-0069_ISO 16, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, station 4. A) Pleopod 1; B) pleopod 2; C) uropodal endopod; D) uropodal exopod.

FIGURE 9 in Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico

FIGURE 9. Mesanthura cocoae sp. nov., holotype, female, 8.7 mm, CIB-0063_ISO 10, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, station 4. A) Pereopod 1; B) palm of pereopod 1; C) pereopod 2; D) pereopod 3; E) pereopod 4; F) pereopod 5; G) pereopod 6.

FIGURE 11 in Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico

FIGURE 11. Colanthura guerreronegroensis sp. nov., holotype, female, 8.7 mm, CIB-0069_ISO 16, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, E4. A) Body, dorsal view; B) pleon and pleotelson; C) antennula; D) antenna; E) mandible; F) maxilla; G) maxilliped.

FIGURE 8 in Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico

FIGURE 8. Mesanthura cocoae sp. nov., holotype, female, 8.7 mm, CIB-0063_ISO 10, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, station 4. A) Body, dorsal view; B) antennula; C) antenna; D) mandible; E) maxilla; F) maxilliped.

FIGURE 7 in Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico

FIGURE 7. Cortezura lluchbeldai sp. nov., holotype, female, 9.8 mm, CIB-0058_ISO 5, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, station 9. A) Pereopod 6; B) Pereopod 7; C) pleopod 1; D) pleopod 2; E) uropodal endopod; F) uropodal exopod.

FIGURE 1 in Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico

FIGURE 1. Map of Guerrero Negro Lagoon, Baja California Peninsula, Mexico. Black dots indicate the different stations where the biological material described in this work was collected.

FIGURE 3 in Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico

FIGURE 3. Amakusanthura lucinae sp. nov., holotype, female, 8 mm, CIB-0055_ISO 2, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, station 5. A) Pereopod 1; B) palm of pereopod 1; C) pereopod 2; D) pereopod 3; E) pereopod 4; F) pereopod 5.

FIGURE 12 in Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico

FIGURE 12. Colanthura guerreronegroensis sp. nov., holotype, female, 8.7 mm, CIB-0069_ISO 16, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, station 4. A) Pereopod 1; B) pereopod 2; C) pereopod 3; D) pereopod 4; E) pereopod 5; F) pereopod 6.

FIGURE 5 in Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico

FIGURE 5. Cortezura lluchbeldai sp. nov., holotype, female, 9.8 mm, CIB-0058_ISO 5, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, station 9. A) Body, dorsal view; B) detail of telson; C) antennula; D) antenna; E) mandible; F) maxilla; G) maxilliped.