Xerces Society Insights on Crabs, Insect Conservation, and Alien Plant Effects

Introduction to Crabs

  • Residents of temperate areas often view crabs primarily as marine creatures, typically encountered during beach trips.

  • In warmer regions, certain crabs, such as Potamonautes sp., have adapted to life on land.

The Xerces Society for Invertebrate Conservation

  • Contact Information:

    • Address: 4828 Southeast Hawthorne Boulevard, Portland, OR 97215

  • Board of Directors:

    • May R. Berenbaum (President)

    • Linda Craig (Treasurer)

    • Sacha Spector (Secretary)

    • Other Board Members: David Johnson, Scott E. Miller, Marla Spivak, Paul R. Ehrlich, Boris Kondratieff, Claire Kremen, John Losey, Thomas Lovejoy, Jerrold Meinwald, Michael G. Morris, Piotr Naskrecki, Paul A. Opler, Dennis Paulson, Robert Michael Pyle, Michael Samways, Cheryl Schultz, Robbin Thorpe

  • Scientific Advisor: E. O. Wilson

  • Membership Information:

    • A $30 per year Xerces Society membership includes a subscription to "Wings" magazine.

  • Cover Photo Information:

    • Photograph of the woollypod milkweed plant (Asclepias eriocarpa) contextualizes the richness of North American milkweed species, which support a diverse community of insects.

Freshwater Crabs and Their Importance

  • Freshwater crabs possess long legs and small bodies that facilitate movement through vegetation and allow them to climb trees.

  • Mentioned Species:

    • Sylviocarcinus pictus (photographed by Piotr Naskrecki).

  • Rediscovery Significance:

    • The chance rediscovery of the purple marsh crab allowed for observations and learning regarding a lesser-known species belonging to a unique lineage of terrestrial crustaceans.

    • Notable Species: A. monodosa and its red-listed relatives found in Guinea, Sierra Leone, and Liberia inhabit the threatened and disturbed habitats within the Upper Guinea forest ecosystem, recognized as a biodiversity hotspot.

  • Conservation Issues:

    • The Upper Guinea forest is a priority conservation area, and unique species, including rare freshwater crabs, face potential extinction threats due to habitat disturbance.

    • Future campsite availability for researchers may become increasingly uncertain.

Research and Expertise

  • Dr. Neil Cumberlidge:

    • Position: Professor in the Biology Department at Northern Michigan University.

    • Focuses on: Taxonomy, systematics, phylogeny, evolution, biogeography, and conservation of African and Madagascan freshwater crabs.

    • Role: Chair of the Species Survival Commission's Freshwater Crabs and Crayfish Specialist Group of the IUCN.

  • Dr. Piotr Naskrecki:

    • Position: Research associate at the Museum of Comparative Zoology, Harvard University.

    • Focuses on: Evolution and systematics of orthopteroid insects and various invertebrate conservation projects, including the IUCN Red List assessment for African katydids and internet resources for invertebrate biologists and conservation practitioners.

  • Acknowledgements:

    • The authors express gratitude to Conservation International for facilitating their research on Africa's freshwater crabs.

The Role of Exotic Plants and Insect Relationships

  • Author: Douglas Tallamy discusses his professional journey in entomology, emphasizing the unintended consequences of cultivating exotic plants while studying plant-insect interactions.

  • Initial Motivation:

    • Tallamy developed a passion for planting various woody landscape plants during graduate school, collecting seeds from ornamental species.

  • Discovery:

    • Despite his enthusiasm for alien ornamentals, Tallamy learned that most insect herbivores are specialized on plants they share an evolutionary history with.

Alien Plant Invasion Consequences

  • Personal Experience:

    • After moving to Pennsylvania, Tallamy observed that 35% of his property comprised aggressive alien plant species, prompting efforts to replace them with natives.

  • Observed Patterns:

    • Alien plants such as multiflora rose, autumn olive, Norway maple, and privet showed minimal insect-induced leaf damage, while native species like red maples and oaks exhibited significant insect feeding.

    • Implication: Ecosystems dominated by alien plants may support fewer insects, which would affect higher trophic levels, particularly birds that rely on insects for food.

  • Ecological Reasoning:

    • Three Reasons native insects are largely unable to utilize introduced plants:

    1. Unpalatability: Many invasive species were favored for their unpalatable characteristics, as noted by Michael Dirr.

    2. Time Lag for Adaptation: Adaptation to new plants requires long evolutionary time. Native insects do not quickly adapt to non-native plants, evidenced by low herbivore species on introduced plants compared to their home regions.

    3. Evolutionary Relationships: Most phytophagous insects have co-evolved with only a few plant lineages, making native plants more suitable food sources.

Research Findings on Native Insect Diets

  • Research Approach:

    • Tallamy and his students collected data on Lepidoptera larvae from all 1,385 plant genera in the mid-Atlantic region to assess larval host relationships.

  • Ranking Results:

    • Findings revealed that native plants like oaks (Quercus) support significantly more Lepidoptera species (534) compared to non-native plants that supported few to zero species.

    • Preferences:

    • Native cherries: 456 species

    • Willows: 455 species

    • Birches: 413 species

    • Alien species like forsythia, golden raintree supported far fewer than five species.

  • Implications for Biodiversity:

    • Neighborhoods with non-native ornamental plants demonstrate less abundant and diverse Lepidoptera populations, critically impacting bird food sources.

Addressing Invasiveness and Biodiversity

  • Alien Plant Dominance:

    • Acknowledging that many individuals defend the use of alien plants, the reality is they often facilitate certain wildlife while displacing others, leading to a loss of native biodiversity.

  • Case Study: Kudzu's impact on native habitats demonstrates how a single invasive species can supplant a diverse range of native plants, thus affecting many associated insect species.

  • Habitat Replacements:

    • The replacement of native plant communities with ornamental non-natives mirrors invasive effects, prompting a reevaluation of horticultural practices.

  • Conclusion:

    • Reciprocal actions towards promoting native plant growth and minimizing invasive species will benefit broader ecological stability and health, by enabling diverse food webs to thrive.

Author Credentials

  • Douglas Tallamy is a professor and chair of the Department of Entomology and Wildlife Ecology at the University of Delaware.

  • He has taught for thirty years and has authored seventy-three research articles.

  • Adaptation: This essay was adapted from Tallamy's book Bringing Nature Home.

  • Note: The information presented highlights crucial connections between native insect diets, the consequences of introducing alien plant species, and broader implications for ecosystem health and biodiversity.