About

Greg Grether is a professor in the Department of Ecology and Evolutionary Biology at UCLA. His research interests encompass behavior, conservation biology, ecology, and evolutionary biology, with a focus on phenotypes and the use of molecular tools. His work involves studying animals that can be easily observed and manipulated in the field, exploring how behavior influences ecological and evolutionary processes. Grether's research emphasizes the importance of behavior in understanding species interactions, particularly interspecific aggression, and how these interactions can drive diversification. He contributes to filling gaps in knowledge about animal aggression and its role in evolution through both empirical and theoretical approaches.

Research topics

• Ecology
• Biology
• Evolutionary biology

Selected publications

• Spatiotemporal Dynamics of Non‐Ecological Speciation in Rubyspot Damselflies (<i>Hetaerina</i> spp.)

  Molecular Ecology · 2025-05-15 · 2 citations

  articleOpen access

  Non-ecological speciation is a common mode of speciation, which occurs when allopatric lineages diverge in the absence of pronounced ecological differences. Yet, relative to other speciation mechanisms, non-ecological speciation remains understudied. Numerous damselfly clades are characterised as non-adaptive radiations (the result of several rounds of non-ecological speciation without subsequent divergence), but there are few damselfly lineages for which we have a detailed understanding of the spatiotemporal dynamics of divergence. Recent phylogeographic analyses demonstrate that American rubyspot damselflies (Hetaerina americana sensu lato) actually comprise at least two cryptic lineages that coexist sympatrically across most of Mexico. To broaden our understanding of the dynamics of diversification to other rubyspot lineages, we investigated the phylogeographic history of smoky rubyspot damselflies (Hetaerina titia) using genomic data collected across Central and North America. Unexpectedly, we found evidence of reproductive isolation between the highly genetically differentiated Pacific and Atlantic lineages of H. titia in a narrow secondary contact zone on the Isthmus of Tehuantepec, Mexico. We then fit models of historical demography to both H. americana sensu lato and H. titia to place these comparisons in a temporal context. Our findings indicate that Pacific and Atlantic lineages of H. titia split more recently than the broadly sympatric lineages within H. americana sensu lato, supporting key assumptions of the non-ecological speciation model and demonstrating that these two pairs of sister lineages are at different stages of the speciation cycle.

  PublisherOA PDFDOI

• Climate underpins continent‐wide patterns of carotenoid‐based feather colour consistent with Gloger's observations

  Journal of Animal Ecology · 2025-03-25 · 2 citations

  articleOpen access

  Animal coloration has long been predicted to vary across geographic and climatic gradients in accordance with a long-standing ecogeographical rule. But further to his widely supported predictions that melanin pigmentation increases towards the Equator, Gloger observed that reds and yellows are more vivid in warm regions and thus more prevalent at lower latitudes, a prediction supported further by Görnitz, who suggested these colours would be more intense in areas with higher rainfall. Yet, studies of the associations between geography or climate and carotenoid-based plumage coloration to test these observations at a continental scale are scarce. Here, we investigated the extent to which yellow and red feather colour varies according to these hypotheses in Pogoniulus tinkerbirds with distributions across sub-Saharan Africa. We tested first for associations of feather colour with geography along latitudinal or elevational gradients, and then for associations with the climatic factors of rainfall and temperature that may underpin colour variation on continental scales. We find evidence consistent with Gloger and Görnitz's observations that more saturated colours and warmer hues at lower latitudes were primarily attributed to a relationship of underpart colour with temperature and rainfall. By contrast, forecrown colour, a trait previously associated with sexual selection, had a more complex association with geography and climate, with red forecrown hue associated with rainfall, but red and yellow intensity showing contrasting patterns with latitude. We highlight the complex nature of carotenoid-based plumage coloration, suggesting that although environmental factors affect the abundance of carotenoid availability, plumage coloration is also influenced by other selective pressures.

  PublisherOA PDFDOI

• Building genomically‐informed demographic models to guide management of invasive hybrids

  Ecological Applications · 2025-10-01

  articleOpen access

  Abstract Invasive species present one of the most challenging threats to native biodiversity, particularly when they hybridize with imperiled native taxa. In California, hybridization between the endangered California tiger salamander (“CTS,” Ambystoma californiense ) and the invasive barred tiger salamander (“BTS,” Ambystoma mavortium ) is one of the best understood examples of this management challenge. Reclusive life history and cryptic hybridization, often on private land, render eradication programs difficult or impossible. This study evaluates hydroperiod management as a tool to conserve and maintain native CTS populations threatened by hybridization. We adapt a recent, empirically informed Bayesian integral projection model (IPM) for CTS to incorporate new results that link genotype and ecology to fitness, and use this individual‐based model to evaluate alternative management scenarios. We found overwhelming support for the importance of hydrology in both native and hybrid populations, where a 10‐day increase in hydroperiod can increase population growth rate () 17% and triple the carrying‐capacity ( K ). We assess hydroperiod management as a strategy to control and contain hybrid introgression, and suggest a three‐pronged strategy. First, for native populations not at risk of hybridization, hydroperiod should be increased to &gt;120 days to support robust populations. Second, within the geographic hybrid zone, hydroperiod should be reduced to limit hybrid populations, maintain vernal pool function, and improve the efficiency of adult hybrid removal. Finally, our models indicate that managers should combine hydroperiod management with rapid field‐based genotyping and hybrid removal, focusing on ponds where hybrids are rare, typically at the leading edge of the hybrid swarm. Efforts should also prioritize high‐intensity surveys and early removal as opposed to long‐duration (10+ years), lower effort surveys. This study demonstrates the value of integrating demographic, genetic, and ecological information to evaluate strategies for endangered species management, and may serve as modeling framework for a wide variety of imperiled species.

  PublisherOA PDFDOI

• Pre-release experience with a heterospecific competitor increases fitness of a translocated endangered species

  Biological Conservation · 2025-04-25 · 3 citations

  articleOpen accessSenior author

  Translocation is a key conservation strategy, with breeding programs increasingly providing animals for release. Despite its growing use, translocation efforts frequently encounter limited success, particularly when captive-born animals are involved. Ex-situ environments may lack cues needed to develop survival behaviors, such as predator avoidance, foraging, and social skills. Although practitioners typically address the lack of predator avoidance through training or predator removal, competitor naivety remains largely overlooked, despite its potential to hinder population establishment by compromising access to resources. We examined the impact of pre-release competitor experience on the Pacific pocket mouse ( Perognathus longimembris pacificus ), one of southern California's most critically endangered mammals. The Pacific pocket mouse is the smallest, and most behaviorally subordinate species in a community of native rodents that compete for resources. We conducted a controlled experiment to test if providing captive-born mice pre-release experience with kangaroo rats ( Dipodomys simulans ) would improve translocation outcomes. We compared fitness and body condition of pocket mice between the two treatments and examined if behavioral change was exhibited before release. Competitor-experienced females gained more weight and had higher survival and reproductive success than controls, with female survival surpassing that of males in both groups. These findings suggest that incorporating competitor experience into conservation breeding programs could improve translocation success. As competition is a common challenge in natural ecosystems, this behavioral intervention could be applicable for a wide range of species. • Conservation translocations often fail due to released animals' behavioral issues. • Captive bred animals are naïve to heterospecific competition, exposure may help. • We test first ever pre-release competitor training, in an endangered small mammal. • Competitor-experienced females had higher fitness than controls and males. • Pre-release competitor experience can substantially improve translocation outcomes.

  PublisherDOI

• CAMERA TRAP FOOTAGE OF ISLAND-ENDEMIC RINGTAIL CONSUMING NEUROTOXIC PORCUPINEFISH

  The Southwestern Naturalist · 2025-10-10

  articleSenior author

  La dieta del cacomixtle norteño (Bassariscus astutus) varía estacionalmente y a lo largo de su extensa distribución. Durante el estudio de la subespecie insular y endémica del cacomixtle norteño (B. a. saxicola) en México, una de nuestras cámaras trampa capturó en video a un cacomixtle consumiendo un pez globo (Diodon holocanthus). No se han descrito peces en la dieta de ninguna otra población de la especie. Esta evidencia resulta sorprendente, considerando que los peces globo contienen una potente neurotoxina (tetrodotoxina) en algunos órganos y espinas. Hasta donde tenemos conocimiento, no existe evidencia de resistencia a tetrodotoxina en mamíferos. Se requiere más investigación para determinar si el linaje insular del cacomixtle norteño ha desarrollado resistencia a la toxina, lo que le permitiría aprovechar una nueva fuente de proteína disponible en las islas.

  PublisherDOI

• Pre-Release Experience with a Heterospecific Competitor Increases Fitness of a Translocated Endangered Species

  SSRN Electronic Journal · 2024-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Sexual selection and speciation

  Elsevier eBooks · 2024-01-01 · 1 citations

  book-chapter1st authorCorresponding
  PublisherDOI

• Spatiotemporal dynamics of non-ecological speciation in rubyspot damselflies ( <i>Hetaerina</i> spp.)

  bioRxiv (Cold Spring Harbor Laboratory) · 2024-12-12 · 2 citations

  preprint

  Abstract Non-ecological speciation is a common mode of speciation which occurs when allopatric lineages diverge in the absence of pronounced ecological differences. Yet, relative to other speciation mechanisms, non-ecological speciation remains understudied. Numerous damselfly clades are characterized as non-adaptive radiations (the result of several rounds of non-ecological speciation), but there are few damselfly lineages for which we have a detailed understanding of the spatiotemporal dynamics of divergence. Recent phylogeographic analyses demonstrate that American rubyspot damselflies ( Hetaerina americana sensu lato) actually comprise at least two cryptic lineages that coexist sympatrically across most of Mexico. To broaden our understanding of the dynamics of diversification to other rubyspot lineages, we investigated the phylogeographic history of smoky rubyspot damselflies ( Hetaerina titia ) using genomic data collected across Central and North America. Unexpectedly, we found evidence of reproductive isolation between the highly genetically differentiated Pacific and Atlantic lineages of H. titia in a narrow secondary contact zone on the Isthmus of Tehuantepec, Mexico. We then fit models of historical demography to both H. americana sensu lato and H. titia to place these comparisons in a temporal context. Our findings indicate that Pacific and Atlantic lineages of H. titia split more recently than the broadly sympatric lineages within H. americana sensu lato, supporting key assumptions of the non-ecological speciation model and demonstrating that these two pairs of sister lineages are at different stages of the speciation cycle.

  PublisherDOI

• Reduction in mutualistic ant aggressive behavior upon sugar supplementation

  Biotropica · 2024-10-16

  articleOpen accessSenior author

  Abstract Mutualistic interactions between species are widespread and important for community structure and ecosystem function. In a changing environment, the proximate mechanisms that maintain mutualisms affect their stability and susceptibility to perturbation. In ant‐plant mutualisms, ants defend their host plants against herbivores or competing plants in exchange for housing or food. While the phenomenon of species exchanging services for resources is well documented, how such arrangements are maintained is not. There are at least four hypothesized mechanisms through which plants use sugar to induce ant defense against herbivores. Three such hypotheses (“deficit”, “fuel for foraging”, “predictable rewards”) predict that the appearance of a new sugar source near the host plant would increase the rate of ant attacks against herbivores, but the fourth hypothesis (“attract and distract”) predicts the opposite. To examine how the mutualism between Triplaris americana and Pseudomyrmex dendroicus would be affected, we simulated the appearance of a novel sugar source at a random half of 34 T. americana trees with P. dendroicus colonies . Compared to control colonies, those with access to the sugar source were less likely to attack herbivorous insects ( Nasutitermes sp. termites). Thus, our findings support the “attract and distract” hypothesis. We infer that this ant‐plant mutualism could be destabilized by the appearance of an alternative sugar source, such as a nectar‐producing plant or honeydew‐excreting insect. More broadly, we conclude that the mechanisms responsible for maintaining mutualistic relationships are relevant for understanding how ecological communities are affected by environmental change. Abstract in Spanish is available with online material.

  PublisherOA PDFDOI

• Data and R code for McEachin, S., Drury, J.P., and Grether, G.F., Competitive displacement and agonistic character displacement, or the ghost of interference competition. Accepted for publication in the <i>The American Naturalist </i>on September 14, 2023

  Figshare · 2023-01-01

  datasetOpen accessSenior author

  This repository contains the data and R code for running all of the statistical analyses and simulations, and also for creating the figures in the manuscript "Competitive displacement and agonistic character displacement, or the ghost of interference competition". The data were collected by the authors in the field in Costa Rica in 2016 and 2017, with permission from the government of Costa Rica (SINAC-MINAE). For further information, please refer to the published manuscript.

  PublisherDOI

Recent grants

• The Evolutionary Consequences of Interspecific Aggression

  NSF · $458k · 2010–2015

• NSFDEB-NERC: Interspecific interference, character displacement and range expansion

  NSF · $857k · 2021–2027

• Territoriality and reproductive interference between species

  NSF · $683k · 2015–2020

Frequent coauthors

• Jonathan P. Drury

  Durham University

  29 shared

• Christopher N. Anderson

  15 shared

• Debra M. Shier

  15 shared

• Gita R. Kolluru

  California Polytechnic State University

  9 shared

• Alexander N. G. Kirschel

  University of Cyprus

  6 shared

• David F. Millie

  6 shared

• Tom Maddox

  6 shared

• Blaire Van Valkenburgh

  6 shared

Education

• Ph.D., Economics

  University of California, Los Angeles

  1992

• M.A., Economics

  University of California, Los Angeles

  1987

• B.A., Economics

  University of California, Los Angeles

  1985