Wayne Sousa - Academia.edu (original) (raw)

Papers by Wayne Sousa

Madroño, Apr 21, 2022

Abstract California, a hotspot of plant biodiversity, is projected to experience a significant in... more Abstract California, a hotspot of plant biodiversity, is projected to experience a significant increase in average temperature by the end of the century, from +1.5°C under low emissions to +4°C under medium-high emissions models. This warming could severely affect unique, endemic ecosystems like the chaparral. Phenotypic plasticity, the capacity of organisms to express different phenotypes in response to environmental cues, may be an important means by which plants adjust to climate change. Here, we examine differentiation in two traits related to climate adaptation, leaf length and trichome density, previously observed to differ qualitatively between coastal and inland populations of Eriogonum fasciculatum subsp. foliolosum (Nutt.) S.Stokes. We quantitatively verify these leaf trait differences, assess whether they are plastic to temperature, and also assess whether coastal and inland populations express this plasticity differently. We performed field collections, established a novel procedure for vegetative propagation of woody cuttings, and grew cuttings and germinated seeds in temperature treatments simulating current conditions and those projected by future climate models. Our results revealed that leaf traits of both populations respond plastically to temperature, and we also found differentiation for the plasticity expressed by the two populations. Population genetic analyses detected limited genetic differentiation and high gene flow between these two populations, indicating that the observed differentiation in plasticity may be locally adaptive. Together, these findings suggest that this system may exemplify genetic accommodation, in which the evolution of plasticity mediates adaptation, and imply that variation in plasticity is relevant to conservation strategies for this plant and other California native chaparral shrubs in the face of climate change.

Parasite Communities: Patterns and Processes, 1990

An individual host is a patch of habitat for a particular stage in the life cycle of a parasite (... more An individual host is a patch of habitat for a particular stage in the life cycle of a parasite (Price, 1980; Holmes and Price, 1986). It contains resources necessary for growth and development of this infecting stage, and for production of the next, usually dispersing, stage. Each individual host is an inherently bounded, discrete habitat, that is isolated from other similar habitat patches by an external environment that is inhospitable to the parasitic stage that infects the host.

Seedling plot network design: description and figures.

Results tables for GLMM and GEE models of seedling survival.

Forest Ecology and Management, 2022

Ecologists have studied ‘mutual aid’ (or facilitation) since at least the time of Kropotkin (1842... more Ecologists have studied ‘mutual aid’ (or facilitation) since at least the time of Kropotkin (1842–1921). But the ‘watchword’ which he heard with such force has not always been heeded, remains poorly understood and is rather loosely defined. A seminal early use comes from Connell and Slatyer (1977), where building on the work of Clements (1916), they used ‘facilitation’ to describe a model of community succession in which pioneer species modify the habitat allowing the colonisation of later ones. While this successional implication remains common in the literature, the word is also applied more broadly to positive interactions between individuals and species. Some authors restrict the term to plant– plant interactions (e.g., Krebs, 2001), while others treat it as synonymous with ‘positive species relationships’ (He et al., 2013), although Munguia et al. (2009) argue that any relationship that does not cause evolutionary changes to both parties is not a true ‘interaction’. Others expa...

Journal of Plant Ecology, 2020

Classical theory predicts that herbivores impact herb assemblages and soil nitrogen (N) cycling t... more Classical theory predicts that herbivores impact herb assemblages and soil nitrogen (N) cycling through selective plant consumption and the deposition of N-rich waste, with effects dependent upon ecosystem N availability. Herbivores are predicted to accelerate N cycling when N availability is high and decelerate cycling when availability is low. However, experimental tests of these theories in natural systems are limited and have yielded contradictory results. California’s widespread chaparral shrublands provide a tractable system in which to test these theories. They are prone to periodic crown fire, which temporarily removes living shrub cover, deposits mineral N on soils and allows diverse herbaceous assemblages to dominate the landscape for 3–5 years. Chaparral is also increasingly vulnerable to herbaceous invasion; mammalian herbivory may limit the establishment of non-native herbs in the shrub understory. We implemented a 2-year herbivore-exclosure experiment (Hopland, CA) to ...

The Bulletin of the Ecological Society of America, 2021

Science, 2020

J oseph ("Joe") H. Connell, a hugely creative ecologist, died on 1 September at the age of 96. Jo... more J oseph ("Joe") H. Connell, a hugely creative ecologist, died on 1 September at the age of 96. Joe had a knack for devising simple yet rigorous ways to uncover the mechanisms behind the patterns and dynamics in natural communities. Perhaps the most influential experimental ecologist of his generation, he articulated theories explaining natural phenomena such as the maintenance of biological diversity. Joe was born on 5 October 1923 in Gary, Indiana. After Pearl Harbor, in 1941, he enlisted in the U.S. Army Air Corps. He was sent to the University of Chicago for training in meteorology and then stationed in the Azores from 1943 to 1945 flying weather survey missions. In 1946, he completed his B.S. in meteorology at the University of Chicago, followed by an M.

Bulletin of the Ecological Society of America, Aug 3, 2012

Trends in Ecology Evolution, 1994

Treatise on Estuarine and Coastal Science, 2011

Mangrove habitats are among the most productive ecosystems on the Earth. Their low vegetational d... more Mangrove habitats are among the most productive ecosystems on the Earth. Their low vegetational diversity belies a remarkable richness of associated species and trophic interactions. This contribution summarizes what is known about these interactions. Information on interaction strengths, top-down versus bottom-up control, and the consequences of species interactions for community structure is only available for a few systems. At a more fundamental level, our understanding of the relative contributions of different sources of primary productivity and the patterns and mechanisms of their exploitation by herbivores, detritivores, and deposit feeders remains quite limited. Even less is known about the movement of carbon, nitrogen, and other elements through mangrove food webs to higher trophic levels. Long-standing paradigms asserting minimal consumption of living plant tissues by herbivores and the paramount role of mangrove detritus as fuel for secondary production of crustaceans and fish are being challenged by data gathered with newer methodologies, most notably, stable isotope analysis. Much remains to be learned about the role of mangroves as nurseries for juvenile life history stages and the trophic links between mangroves and neighboring ecosystems. Ongoing and future investigations of these processes that employ a balanced mix of quantitative observation and field experiments promise to generate exciting new insights about mangrove community and ecosystem processes, and at the same time inform general food-web theory.

Trends in ecology & evolution, 1994

What processes account for the structure and dynamics of helminth parasite assemblages within ver... more What processes account for the structure and dynamics of helminth parasite assemblages within vertebrate and invertebrate hosts? Attempts to answer this question form the basis for the emerging subdiscipline of parasite community ecology. Negative interspecific interactions strongly affect the distribution and abundance of parasites in some systems, but only intermittently, if ever, in others. Empirical results provide only mixed support for recent theories that attempt to explain this variation.

The Ecology of Natural Disturbance and Patch Dynamics, 1985

... deals primarily with the effects of natural disturbance on the assemblages of sessile algae a... more ... deals primarily with the effects of natural disturbance on the assemblages of sessile algae and invertebrates that occupy the surfaces of intertidal rocks. ... While the majority of the examples in this chapter are drawn from studies of temperate rocky shores, this does not imply that ...

Lecture Notes in Geoinformation and Cartography

Trends in Ecology & Evolution, 1994

Photogrammetric Engineering & Remote Sensing, 2008

Tropical forests in many areas of Central and South America experience strong seasonality in clim... more Tropical forests in many areas of Central and South America experience strong seasonality in climatic variables such as rainfall, solar radiation, wind speed, and relative humidity. Such seasonality is typical of the mangrove forests we study along the Caribbean coast of Panama. Tied to this environmental variation are changes in leaf phenology and physiology that can affect the spectral properties of leaves and thus our ability to discriminate canopies of differing species composition. The goals of this study were twofold. First, we compared the efficacy of three different classification methods for discriminating mangrove canopies, including a back-propagation, feed-forward neural network classifier with two hidden layers of 24 and 12 neurons (hereafter, BP:24:12), a newly developed clusteringbased neural network classifier (CBNN), and a maximum likelihood classifier (MLC). Comparisons were made with and without added textural information. Our second aim was to compare the absolute and relative discrimination abilities of these methods when applied to images of the same forest acquired in different seasons. Two sets of Ikonos images acquired in February (dry season) and May (early wet season) 2004 were analyzed in this study. When only spectral information was considered, MLC and CBNN discriminated differences in canopy species composition with higher accuracy than the BP:24:12 method. When second-order textural information was also taken into account, CBNN outperformed MLC and presented the best classification accuracy, i.e., kappa value equaled 0.93. Analyses of the wet season (May) image were consistently more accurate in discriminating mangrove canopies of differing species composition than analyses of the dry season (February) image, regardless of the classification method or the inclusion of textural information.

Oikos, 1999

... general pattern in mangroves? Wayne P. Sousa and Betsy J. Mitchell Sousa, WP and Mitchell, BJ... more ... general pattern in mangroves? Wayne P. Sousa and Betsy J. Mitchell Sousa, WP and Mitchell, BJ 1999. The effect of seed predators on plant distributions: is there a general pattern in mangroves? - Oikos 86: 55-66. ... WP Sousa and BJ Mitchell, Dept of Integrative Biology, Univ. ...