Macroecology and consilience

Consilience means that all fields of human knowledge should be internally consistent. Within the broad span of the ecological and evolutionary sciences, there are many fields that seem only remotely related conceptually. Macroecology has emerged as a research programme that focuses on statistical patterns of ecological and biogeographically relevant traits among different species within a taxon. The concepts needed to understand these patterns require the interface of disciplines as different as systematics, ecosystem ecology, palaeontology and community ecology. By building conceptual links among a wide range of disciplines, macroecology is contributing, and will continue to contribute, to the growing realization that all of biology is indeed consilient.     

A cross-scale framework to support a mechanistic understanding and modelling of marine climate-driven species redistribution,from individuals to communities

Climate-driven species redistribution is pervasive and accelerating, yet the complex mechanisms at play remain poorly understood. The implications of large-scale species redistribution for natural systems and human societies have resulted in a large number of studies exploring the effects on individual species and ecological communities worldwide. Whilst many studies have investigated discrete components of species redistribution, the integration required for a more complete mechanistic understanding is lacking. In this paper, we provide a framework for synthesising approaches to more robustly understand and predict marine species redistributions. We conceptualise the stages and processes involved in climate-driven species redistribution at increasing levels of biological organisation, and synthesize the laboratory, field and modelling approaches used to study redistribution related processes at individual, population and community levels. We then summarise links between scales of biological organisation and methodological approaches in a hierarchical framework that represents an integrated mechanistic assessment of climate-driven species redistributions. In a rapidly expanding field of research, this framework provides direction for: 1) guiding future research, 2) highlighting key knowledge gaps, 3) fostering data exchange and collaboration between disciplines and 4) improving shared capacity to predict and therefore, inform the proactive management of climate impacts on natural systems.     

Macroecology meets macroevolution: evolutionary niche dynamics in the seaweed Halimeda

Aim Because of their broad distribution in geographical and ecological dimensions, seaweeds (marine macroalgae) offer great potential as models for marine biogeographical inquiry and exploration of the interface between macroecology and macroevolution. This study aims to characterize evolutionary niche dynamics in the common green seaweed genus Halimeda, use the observed insights to gain understanding of the biogeographical history of the genus and predict habitats that can be targeted for the discovery of species of special biogeographical interest. Location Tropical and subtropical coastal waters. Methods The evolutionary history of the genus is characterized using molecular phylogenetics and relaxed molecular clock analysis. Niche modelling is carried out with maximum entropy techniques and uses macroecological data derived from global satellite imagery. Evolutionary niche dynamics are inferred through application of ancestral character state estimation. Results A nearly comprehensive molecular phylogeny of the genus was inferred from a six‐locus dataset. Macroecological niche models showed that species distribution ranges are considerably smaller than their potential ranges. We show strong phylogenetic signal in various macroecological niche features. Main conclusions The evolution of Halimeda is characterized by conservatism for tropical, nutrient‐depleted habitats, yet one section of the genus managed to invade colder habitats multiple times independently. Niche models indicate that the restricted geographical ranges of Halimeda species are not due to habitat unsuitability, strengthening the case for dispersal limitation. Niche models identified hotspots of habitat suitability of Caribbean species in the eastern Pacific Ocean. We propose that these hotspots be targeted for discovery of new species separated from their Caribbean siblings since the Pliocene rise of the Central American Isthmus.     

Diversity,Body Mass,and Latitudinal Gradients in Primates

We examined latitudinal gradients in central value and diversity of body mass of primates to increase understanding of the Forster effect (decrease in taxonomic diversity with increasing latitude) and the Bergmann effect (increase of body mass with latitude). Data are from the literature. We used species’ median body mass of females and mid-latitude (N = 164). We account for phylogenetic effects with comparative analysis by independent contrasts and analysis at differing taxonomic levels. Globally, diversity of both taxonomy and body mass declined significantly with increasing latitude. The decrease in the range of body masses with increasing latitude was caused mainly by the absence of several small-bodied clades at higher latitudes, but also by the absence there of great apes. The disappearance of the small-bodied clades caused an increase in median body mass with latitude, i.e., primates show a significant taxon-wide Bergmann effect, including with phylogenetic correction. Within the Primates, the Bergmann effect was significant within taxa that extend from the equator the farthest into temperate regions: the Old World infraorder Catarrhini, family Cercopithecidae, and subfamily Cercopithecinae; the Asian Cercopithecidae; and in Southeast Asian Sunda, Macaca. The results accord with hypotheses for the Forster effect that latitudinal gradients in taxonomic diversity result from high rates of speciation in the tropics, and ecological, and therefore evolutionary, constraints on diversity at higher latitudes. For the Bergmann effect, the results support energetic hypotheses that the very largest-bodied and the small-bodied taxa cannot survive the long periods of limited resources at higher latitudes.     

Macroecology, global change and the shadow of forgotten ancestors

Many recent studies have evaluated how global changes will affect biodiversity, and have mainly focused on how to develop conservation strategies to avoid, or at least minimize, extinctions due to shifts in suitable habitats for the species. However, these complex potential responses might be in part structured in phylogeny, because of the macroecological traits underlying them. In this comment, we review recent analytical developments in phylogenetic comparative methods that can be used to understand patterns of trait changes under environmental change. We focus on a partial regression approach that allows for partitioning the variance of traits into a fraction attributed to a pure ecological component, a fraction attributed to phylogenetically structured environmental variation (niche conservatism) and a fraction that may be attributed to phylogenetic effects only. We then develop a novel interpretation for linking these components for multiple traits with potential responses of species to global environmental change (i.e. adaptation, range shifts or extinctions). We hope that this interpretation will stimulate further research linking evolutionary components of multiple traits with broad-scale environmental changes.     

Avian host composition,local speciation and dispersal drive the regional assembly of avian malaria parasites in South American birds

Identifying the ecological factors that shape parasite distributions remains a central goal in disease ecology. These factors include dispersal capability, environmental filters and geographic distance. Using 520 haemosporidian parasite genetic lineages recovered from 7,534 birds sampled across tropical and temperate South America, we tested (a) the latitudinal diversity gradient hypothesis and (b) the distance–decay relationship (decreasing proportion of shared species between communities with increasing geographic distance) for this host–parasite system. We then inferred the biogeographic processes influencing the diversity and distributions of this cosmopolitan group of parasites across South America. We found support for a latitudinal gradient in diversity for avian haemosporidian parasites, potentially mediated through higher avian host diversity towards the equator. Parasite similarity was correlated with climate similarity, geographic distance and host composition. Local diversification in Amazonian lineages followed by dispersal was the most frequent biogeographic events reconstructed for haemosporidian parasites. Combining macroecological patterns and biogeographic processes, our study reveals that haemosporidian parasites are capable of circumventing geographic barriers and dispersing across biomes, although constrained by environmental filtering. The contemporary diversity and distributions of haemosporidian parasites are mainly driven by historical (speciation) and ecological (dispersal) processes, whereas the parasite community assembly is largely governed by host composition and to a lesser extent by environmental conditions.     

Habitat heterogeneity drives the host‐diversity‐begets‐parasite‐diversity relationship: evidence from experimental and field studies

Despite a century of research into the factors that generate and maintain biodiversity, we know remarkably little about the drivers of parasite diversity. To identify the mechanisms governing parasite diversity, we combined surveys of 8100 amphibian hosts with an outdoor experiment that tested theory developed for free‐living species. Our analyses revealed that parasite diversity increased consistently with host diversity due to habitat (i.e. host) heterogeneity, with secondary contributions from parasite colonisation and host abundance. Results of the experiment, in which host diversity was manipulated while parasite colonisation and host abundance were fixed, further reinforced this conclusion. Finally, the coefficient of host diversity on parasite diversity increased with spatial grain, which was driven by differences in their species–area curves: while host richness quickly saturated, parasite richness continued to increase with neighbourhood size. These results offer mechanistic insights into drivers of parasite diversity and provide a hierarchical framework for multi‐scale disease research.     

Ecological Patterns and Biological Invasions: Using Regional Species Inventories in Macroecology

Macroecology depends heavily on a comparative methodology in order to identify large-scale patterns and to test alternative hypotheses that might generate such patterns. With the advent and accessibility of large electronic databases of species and their life history and ecological attributes, ecologists have begun seeking generalities, and examining large-scale ecological hypotheses involving core themes of range, abundance and diversity. For example, combinations of ecological, life history and phylogenetic data have been analysed using large species sets to test hypotheses in invasion biology. Analysis of regional species inventories can contribute cogently to our understanding of invasions. Here we examine several ways in which database analysis is effective. We review 19 studies of comparative invasions biology, each using >100 species of plants in their analyses, and show that invader success is linked to seven correlates: short life cycle, abiotic (mostly wind) dispersal, large native range size, non-random taxonomic patterns (emphasizing certain families or orders), presence of clonal organs, occupying disturbed habitats, and earlier time of introduction. These phylogenetically influenced, comparative analyses using regional species inventories are only just beginning and have much potential.     

Bird species numbers in an archipelago of reeds at Lake Velence, Hungary

1 Bird species numbers were studied on 109 reed islands at Lake Velence, Hungary, in the 1993 and 1994 breeding seasons. The aim was to describe and account for the abundance and distribution patterns of the bird species. 2 It was expected that an exponential model would fit the calculated species–area curves. However, for the 1993 data, both the power function (LogS ~ LogArea) and the exponential (S ~ LogArea) models did so, while the power function, exponential and linear (S ~ A) models fitted the curves for the 1994 data. 3 The results showed that the pattern was not random: a collection of small islands held more species than a few large islands with the same total area. 4 The relative species richness of small islands is a result of the preference of most common passerine bird species for the edges of reed islands. Most individuals were found in the first 5 m of the reedbed, and no edge avoidance was detected on a local spatial scale. Large, rarer species (e.g. Great White Egret), however, were found to be dependent on large reed islands. 5 Comparison of results with two other studies on bird communities of reed islands revealed that the type of landscape matrix (e.g. deep water, shallow water or agricultural lands) among reed patches significantly influences bird communities. Deep water was dominated by grebes and coot, shallow water by reed‐nesting passerines, and farmed areas by reed‐ and bush‐nesting passerines.     

Sampling Effects and Host Ranges in Australian Mistletoes

The number of host species utilized by Australian mistletoe species increases with their geographic range sizes. Rather than resulting from deterministic processes, we demonstrate that this pattern results from wider-ranging species being sampled more efficiently, and we discuss how sampling effects might be addressed in future analyses of mistletoe biogeography.     

Floristics of forests across low nutrient soils in Sulawesi,Indonesia

The island of Sulawesi formed from the joining of proto-islands roughly three million years ago. Regions of zoological endemism, corresponding to the proto-islands, have been reported. Sulawesi's tree communities, however, remain poorly documented. In better-studied tropical regions, soil types similar to those found in Sulawesi often have distinctive tree communities. To gather data on Sulawesi's tree communities, we established ten (0.25 ha) plots on four soil types across three regions. We documented diversity, endemism, dominance, and species composition. Linear models of species composition showed greater influence of geographic distance rather than soil, and no relationship with climate. This suggests that the legacy of Sulawesi's formation may have influenced tree communities more so than the soil types we sampled. Most of our plots were on stressful soil types making it difficult to conclude on the importance of edaphic specialization in the Sulawesi tree flora. The lack of climatic effects reflects Sulawesi's position within the wet tropics where the small climatic differences are unlikely to have large influence on tree communities.     

Faunal breaks and species composition of Indo-Pacific corals: the role of plate tectonics,environment and habitat distribution

Species richness gradients are ubiquitous in nature, but the mechanisms that generate and maintain these patterns at macroecological scales remain unresolved. We use a new approach that focuses on overlapping geographical ranges of species to reveal that Indo-Pacific corals are assembled within 11 distinct faunal provinces. Province limits are characterized by co-occurrence of multiple species range boundaries. Unexpectedly, these faunal breaks are poorly predicted by contemporary environmental conditions and the present-day distribution of habitat. Instead, faunal breaks show striking concordance with geological features (tectonic plates and mantle plume tracks). The depth range over which a species occurs, its larval development rate and genus age are important determinants of the likelihood that species will straddle faunal breaks. Our findings indicate that historical processes, habitat heterogeneity and species colonization ability account for more of the present-day biogeographical patterns of corals than explanations based on the contemporary distribution of reefs or environmental conditions.     

Ecological memory at millennial time-scales: the importance of data constraints,species longevity and niche features

Ecological memory describes how antecedent conditions drive the dynamics of an ecological system. Palaeoecological records are paramount to understand ecological memory at millennial time-scales, but the concept is widely neglected in the literature, and a formal approach is lacking. Here, we fill such a gap by introducing a quantitative framework for ecological memory in palaeoecology, and assessing how data constraints and taxa traits shape ecological memory patterns. We simulate the population dynamics and pollen abundance of 16 virtual taxa with different life and niche traits as a response to an environmental driver. The data is processed to mimic a realistic sediment deposition and sampled at increasing depth intervals. We quantify ecological memory with Random Forests, and assess how data properties and taxa traits shape ecological memory. We find that life-span and niche features modulate the relative importance of the antecedent values of the driver and the pollen abundance over periods of 240 yr and longer. Additionally, we find that accumulation rate and decreasing pollen-sampling resolution inflate the importance of antecedent pollen abundance. Our results suggest that: 1) ecological memory patterns are sensitive to varying accumulation rates. A better understanding on the numerical basis of this effect may enable the assimilation of ecological memory concepts and methods in palaeoecology; 2) incorporating niche theory and models is essential to better understand the nature of ecological memory patterns at millennial time-scales. 3) Long-lived generalist taxa are highly decoupled from the environmental signal. This finding has implications on how we interpret the abundance-environment relationship of real taxa with similar traits, and how we use such knowledge to forecast their distribution or reconstruct past climate.     

Marine biogeography and ecology: invasions and introductions

Although biogeography and ecology had previously been considered distinct disciplines, this outlook began to change in the early 1990s. Several people expressed interest in creating a link that would help ecologists become more aware of external influences on communities and help biogeographers realize that distribution patterns had their genesis at the community level. They proposed an interdisciplinary approach called macroecology. This concept has been aided by the advent of phylogeography, for a better knowledge of genetic relationships has had great interdisciplinary value. Two areas of research that should obviously benefit from a macroecological approach are: (1) the question of local vs. regional diversity and (2) the question of whether invader species pose a threat to biodiversity. The two questions are related, because both deal with the vulnerability of ecosystems to penetration by invading species. Biogeographers, who have studied the broad oceanic patterns of dispersal and colonization, tend to regard isolated communities as being open to invasion from areas with greater biodiversity. It became evident that many wide‐ranging species were produced in centres of origin, and that the location of communities with respect to such centres had a direct effect on the level of species diversity. Ecologists, in earlier years, thought that a community could become saturated with species and would thereafter be self‐sustaining. But recent research has shown that saturation is probably never achieved and that the assembly of communities and their maintenance is more or less dependent on the invasion of species from elsewhere. The study of invasions that take place in coastal areas, usually the result of ship traffic and/or aquaculture imports, has special importance due to numerous opinions expressed by scientists and policy‐makers that such invasions are a major threat to biodiversity. However, none of the studies so far conducted has identified the extinction of a single, native marine species due to the influence of an exotic invader. Furthermore, fossil evidence of historical invasions does not indicate that invasive species have caused native extinctions or reductions in biodiversity.     

Variable colour patterns indicate multidimensional,intraspecific trait variation and ecological generalization in moths

Animal colour patterns long have provided information about key processes that drive the ecological and evolutionary dynamics of biological diversity. Theory and empirical evidence indicate that variation in colour patterns and other traits among individuals generally improves the performance of populations and species, for example by reducing predation risk, increasing establishment success, improving resilience to environmental change, and decreasing risk of extinction. However, little is known about whether and how variation in colour pattern among species is associated with variation in other phenotypic dimensions. To address this issue, we analysed associations of colour pattern with morphological, behavioural and life-history traits on the basis of data for nearly 400 species of noctuid moths. We found that moths with more variable colour patterns had longer flight activity periods, more diverse habitats and a greater number of host plant species than species with less variable colour patterns. Variable coloration in adult noctuid moths therefore can be considered as indicative of broader niches and generalist diets. Colour pattern variability was not significantly associated with overwintering stage or body size (wing span), and it was independent of whether the colour pattern of the larvae was non-variable, variable or highly variable. Colour pattern variation during the larval stage tended to increase as the duration of the flight activity period increased, but was independent of the length of the larval period, diet breadth and habitat use. The realization that information on colour pattern variation in adult moths, and possibly other organisms, offers a proxy for niche breadth and dietary generalization can inform management and conservation biology.     

Connections between ecology,biogeography, and paleobiology: Relationship between local abundance and geographic distribution in fossil and recent molluscs

Summary We used data on Contemporary and Pleistocene molluscs at one site in the Gulf of California to evaluate and extend earlier ideas about the relationship between local abundance and geographic distribution. For each species whose shells occurred in one Recent and two Pleistocene deposits, we measured its abundance in the sample and relative latitudinal position within its contemporary geographic range. Species near the edges of their ranges showed uniformly low abundances, whereas those near the centres exhibited a wide range of abundances. Species near the edges of their ranges also appear to have exhibited greater changes in abundance, including more colonization and extinction events, between the Pleistocene interglacial sample and the Recent one. The constraint of location in the geographic range on maximal local and regional abundance appears to offer an example of a connection between patterns and processes on local, regional, and geographical scales. Characteristics of community structure, such as relative abundance of individual species and frequency of local co-existence of multiple species, may be influenced by the location of the sample site with respect to the geographic ranges of the constituent species. These results demonstrate emergent, statistical features of population ecology and community organization that are manifest over geographic space and evolutionary time.     

Latitudinal patterns and regionalization of plant diversity along a 4270‐km gradient in continental Chile

According to the global latitudinal diversity gradient, a decrease in animal and plant species richness exists from the tropics towards higher latitudes. The aim of this study was to describe the latitudinal distribution patterns of Chilean continental flora and delineate biogeographic regions along a 4270‐km north–south gradient. We reviewed plant lists for each of the 39 parallels of continental Chile to build a database of the geographical distribution of vascular plant species comprising 184 families, 957 genera and 3787 species, which corresponded to 100%, 94.9% and 74.2% of the richness previously defined for Chile, respectively. Using this latitudinal presence–absence species matrix, we identified areas with high plant richness and endemism and performed a Cluster analysis using Jaccard index to delineate biogeographic regions. This study found that richness at family, genus and species levels follow a unimodal 4270‐km latitudinal distribution curve, with a concentration of richness in central Chile (31–42°S). The 37th parallel south (central Chile) presented the highest richness for all taxonomic levels and in specific zones the endemism (22–37°S) was especially high. This unimodal pattern contrasts the global latitudinal diversity gradient shown by other studies in the Northern hemisphere. Seven floristic regions were identified in this latitudinal gradient: tropical (18–22°S), north Mediterranean (23–28°S), central Mediterranean (29–32°S), south Mediterranean (33–37°S), north temperate (38–42°S), south temperate (43–52°S) and Austral (53–56°S). This regionalization coincides with previous bioclimatic classifications and illustrates the high heterogeneity of the biodiversity in Chile and the need for a reconsideration of governmental conservation strategies to protect this diversity throughout Chile.