ECOLOGY & EVOLUTION

My primary research broadly spans ecology and evolutionary biology, with specific focus on understanding how ecological and microevolutionary processes may explain broader macroevolutionary patterns. At the basis of this is understanding the mechanisms and dynamics that allow species to coexist and novel communities to form.

Ecological opportunity & Adaptive radiation

(Above) There are many ways that ecological opportunity may appear resulting in adaptive radiations, but is it possible to identify prior to diversification? From Stroud and Losos (2016) Annual Review of Ecology, Evolution, & Systematics
Adaptive radiation, the evolutionary divergence of members of a single phylogenetic lineage into a variety of different adaptive forms, is widely attributed as a predominant mode of biological diversification.
​
One potential trigger of this process, "ecological opportunity" - the availability of ecologically accessible resources that may be evolutionarily exploited - has been widely invoked as a potential key to understanding when and how adaptive radiation occurs. However, what the term actually means, much less how it mechanistically leads to adaptive diversification, is currently debated.

Recent recognition that evolutionary change can occur rapidly and on a timescale commensurate with ecological processes suggests that it is time to synthesize ecological and evolutionary approaches to the study of community assembly and evolutionary diversification. 
Underlying the process of adaptive radiation are the mechanisms which allow species to coexist following speciation. The classic scenario of adaptive radiation postulates that adaptive divergence occurs during secondary contact following allopatric speciation, and is supported in many of the the archipelago models (e.g. Darwin's finches).  

My research capitalizes on the assembly of non-native Anolis 
lizards in South Florida. In some cases, multiple species of the same "ecomorph" class (ie. similar in ecology, morphology, and behaviour) exist independently in allopatry. This replicates the conditions following an speciation event in the early stages of adaptive radiation. Recently, some of these species have come into contact and coexist in sympatry. 

Once sympatric populations reach their carrying capacity, species may compete for resources. As a result, species may respond behaviourally and diverge in their resource use to minimize interspecific competition. Natural selection may then cause the species to diverge phenotypically to adapt to their new resource utilization regimes ( their "niches"). This is the process of ecological character displacement, and is considered a fundamental process in the production of phenotypic diversity in adaptive radiations. I am investigating how ecologically-similar Anolis species coexist - ie. if resource partitioning is occurring - and if so, does this lead to character displacement as predicted?

species coexistence & character displacement

(Above) A conceptual representation of established Anolis lizard species and their preferred microhabitats which coexist in South Florida. From top to bottom: A. equestris (Cuba), A. garmani (Jamaica), A. carolinensis (USA), A. distichus (Hispaniola), A. cristatellus (Puerto Rico), A. sagrei (Cuba) 

species distributions & Community Assembly

(Above) Species distributions and community assembly of introduced ​Anolis lizards in Bermuda. From Stroud et al. (2019) Ecology
Species distributions are predominantly assumed to be governed by species' abiotic characteristics or geographic constraints. Much less empirical evidence exists for the relative importance of biotic interactions in determining distributions and range dynamics, despite being frequently implemented as a controlling factor.

Using a multivariate approach of characterizing ecology, morphology, and behaviour, I am investigating the role of both biotic (interspecific) interactions and priority effects in determining the range dynamics of newly introduced species, and subsequent community assembly patterns. This research also capitalizes on the introduction Anolis lizards to many places outside of their native range. I currently have research projects on these topics established in South Florida, Bermuda (with Sean Giery), and Costa Rica (with Michelle Thompson).
Understanding the mechanistic basis of character displacement is a fundamental yet often overlooked aspect of the process. Interspecific competition for a limited resource, or resources, is usually inferred from various responses in either behaviour or population demographics. Alongside Dr. Rob Heathcote I am investigating the underlying social dynamics of character displacement. Additionally, using combinations of species with a mixture of both allopatric and sympatric populations we are investigating the evolution of sociality in Anolis lizards.
(Above) A mixed social network of two coexisting Anolis species in Miami, FL.

mixed species social networks

(Above) An adult male Cuban brown anole (A. sagrei) performing dewlap extension displays while temporarily marked during an observational study of social networks.
Relevant publications:

- Stroud, J. T., & Losos, J.B. (2016) Ecological Opportunity and Adaptive Radiation. Annual Review of Ecology, Evolution & Systematics, 47: 507-532 PDF
- Kolbe, J.J., VanMiddlesworth, P., Battles, A.C., Stroud, J.T., Buffum, B., Forman, R.T.T., Losos, J.B. (2016) Determinants of spread in an urban landscape by an introduced lizard. Landscape Ecology, ​31(8): 1795-1813 PDF
- Stroud, J.T., Bush, M.R., Ladd, M.C., Nowicki, R.J., Shantz, A.A., and Sweatman, J. (2015) Is a community still a community? Reviewing definitions of key terms in community ecology. Ecology & Evolution: doi: 10.1002/ece3.1651 PDF
- Gillespie, G.R., Howard, S., Stroud, J.T., Ul-Hassanah, A., Campling, M., Lardner, B., Scroggie, M., Kusrini, M. (2015) Responses of a tropical herpetofauna community to anthropogenic disturbance and natural habitat variation in Sulawesi, Indonesia. Biological Conservation, 192(2015): 161-173 doi: 10.1016/j.biocon.2015.08.034 PDF
- Rehm, E., Feeley, K.J., Stroud, J.T. (2015) Losing your edge: climate change and the conservation value of range-edge populations. Ecology & Evolution, doi: 10.1002/ece3.1645 PDF
- Stroud, J.T., and Feeley, K.J. (2015) A downside of diversity? A response to Gallagher et al. Trends in Ecology and Evolution, 30(6): 296-297 PDF
- Feeley, K.J., Rehm, E., Stroud, J.T. (2014) There are many barriers to species migrations. Frontiers of Biogeography 6(2): fb_22006 PDF​