Lynx spiders (family Oxyopidae) are some of my favorites.  They’re big, charismatic, and colorful.  The family is a distinctive one with only 3 genera and 18 species in North America.  Lynx spiders have prominent, long, straight spines on the legs, and a characteristic hexagonal arrangement of the [...]]]> Green Lynx Spider (Peucetia viridans)
Family: Oxyopidae

Lynx spiders (family Oxyopidae) are some of my favorites.  They’re big, charismatic, and colorful.  The family is a distinctive one with only 3 genera and 18 species in North America.  Lynx spiders have prominent, long, straight spines on the legs, and a characteristic hexagonal arrangement of the eyes (which is somewhat visible in the second image below).

During my recent South Carolina field work, I frequently found the Green Lynx Spider (common throughout the south) on vegetation in open pine savannas and meadows.  These sit-and-wait predators do not spin a web, but use their long forelegs to capture prey items.

Late summer is the mating season for these spiders. Females build egg sacs, which they attach to the plant substrate, sometimes protecting the egg sac by constructing a tied-leaf shelter around it (Willey & Adler 1989). Some, but not all, females guard the egg sac against predation until the young emerge (about 2 weeks). Spiderlings emerge from the egg sacs in autumn and overwinter as early instars, before reaching maturity the following season (at around 300 days).

Lynx Spiders feed on both herbivorous insects and pollinating insects, so the benefit to a flowering plant of hosting the spider is unclear, with reductions in herbivory potentially offset by reductions in pollination and fruit set. Some species of Peucetia in the neotropics live and forage exclusively on plants that bear glandular trichomes.  Studies indicate that when prey is scarce, the spiders eat dead insects that adhere to the sticky trichomes.  The presence of the spider reduces rates of herbivory on the host plant without having a significant impact on pollination (Romero et al. 2008).  Thus, the relationship is thought to be a facultative mutualism.  Studies of the Green Lynx Spider, however, indicate that Hymenoptera and Diptera (potential pollinators) are the most frequently consumed prey items (Randall 1982, Willey & Adler 1989), and that the spiders often forage on plant blossoms, so this species may not improve fitness of its host plant.  Indeed, my observations of the species in the field have been primarily on blossoms, where it might be expected that pollinating flies and wasps would be the chief prey.

References Cited:

Randall, J.B. 1982. Prey Records of the Green Lynx Spider, Peucetia viridans (Hentz) (Araneae, Oxyopidae). Journal of Arachnology 10(1): 19-22.

Romero, G.Q., J.C. Souza, and J. Vasconcellos-Neto. 2008. Anti-herbivore protection by mutualistic spiders and the role of plant glandular trichomes. Ecology 89(11): 3105-3115.

Willey, M.B. and P.H. Adler. 1989. Biology of Peucetia viridans (Araneae, Oxyopidae) in South Carolina, with Special Reference to Predation and Maternal Care. Journal of Arachnology 17(3): 275-284.

Fishing in the [...]]]> I’m headed to the Catskills to enjoy the woods and the river for a few days.  Last year I did a lot of botanizing, mothing, and bee photography.  Hopefully this year will be even better!

Fishing in the Catskills

What often gets lost in the excitement surrounding “green” [...]]]> Renewable.  Sustainable.  Green.

All of these buzzwords make us feel good about our progress toward mainstreaming alternative energy sources.  We need to power an increasingly energy-hungry world in the face of global climate change, and we all know that fossil fuels are not the solution.

What often gets lost in the excitement surrounding “green” energy, though, is that these technologies are not free from collateral damage to biodiversity and wildlife habitats.  Wind turbines atop Appalachian ridges, for instance, may impact unique mountain-top habitats, and they are known to kill birds and large numbers of migrating bats.  As pressure has been building on wind farm operators to address this problem, basic steps are being taken to help reduce the impact.  Common sense solutions like shutting down the turbines on relatively calm nights are apparently effective at reducing bat kills, for example.

Biofuels are not without their problems, either, but the problems have largely gone unrecognized, and the solutions are not as straightforward.  From a climate change perspective, one major issue is the increase in emissions caused by land use changes associated with biofuel production.  This is the focus of a current campaign by the Union of Concerned Scientists.  At the “Take Action” section of their site, you can personalize and send a letter to the EPA, urging the agency to consider land use changes when calculating life-cycle analyses of biofuels for the agency’s Renewable Fuels Standard (RFS).

What the UCS letter doesn’t directly address is the impact of those same land use changes on other ecosystem services, wildlife habitat, and biodiversity.  European studies have shown that production of biofuel crops such as corn in the amounts necessary to meet EU targets is generating significant negative impacts on biodiversity.

The production of so-called second-generation biofuels from grasses is somewhat less detrimental, but still far from ideal.  As cellulosic biofuel production becomes more cost-effective and energy efficient, switchgrass, a high-yield, perennial grass, is poised to become an important commodity here in the U.S.

Switchgrass (left) is poised to surpass Corn (right) as the commodity of choice for production of ethanol for biofuel. Photo by USDA ARS Photo Unit, USDA Agricultural Research Service, Bugwood.org (used under a Creative Commons 3.0 Attribution License)

Switchgrass (Panicum virgatum) is a tall, native warm-season grass that was once widespread throughout the American tallgrass prairie.  Today, many cultivars are available, and the species is used for conservation plantings and wildlife habitat, providing valuable food and cover for birds and other wildlife.  So what’s the problem?  When grown in a monoculture, as required for harvesting for biofuels, switchgrass is only marginally better wildlife habitat than corn, or any other crop.

Native prairies were historically very diverse plant communities, with species composition maintained by periodic fires.  Structurally, native grasslands varied in density and height based on fire history, soils, and other factors.  Many grassland birds of conservation concern require patchy bunchgrasses with some bare ground in between plants.  Native bees require a diversity of wildflowers that bloom at different times throughout the year, as well as access to bare soils for nesting.  Butterflies all require different species of hostplants on which their caterpillars can grow.  In short, grassland biodiversity depends on both structural and species diversity of the plant community.  Monocultures just don’t cut it.

Grasshopper Sparrow (Ammodramus savannarum) and other grassland birds are at risk from high biofuel commodity prices. Photo (c) Jeffrey A. Gordon

So what’s at stake?  The concern of many conservationists (myself included) is the potential conversion of privately-owned land that is currently enrolled in federal conservation programs to switchgrass monocultures for biofuel production over the next couple of decades.  Over 33.5 millions acres are currently enrolled in the USDA program called CRP (Conservation Reserve Program), which pays farmers an annual rental rate for retiring land from crop production and planting it to wildlife cover.  CRP contracts typically tie up the land for 10 to 15 years.

Currently, CRP land management is governed by contract stipulations that prohibit disturbance during the breeding season, and encourage wildlife use of the acreage.  Many studies have shown that CRP land is vital to sustaining grassland bird populations.  Pollinating insects, reptiles and amphibians, and other fauna benefit from these habitats as well.

According to USDA figures, almost 60% of the current active acreage in CRP will see contracts expire by the end of 2013.  With the signing of the 2008 Food Conservation and Energy Act (aka the Farm Bill) the CRP cap (maximum acreage to be enrolled in CRP) was already reduced from 39.2 million acres to 32 million acres beginning in 2010.  Thus a mandated net loss of over 4% of current active CRP acreage is already slated to occur in the near future.

While some of the expiring contracts will be renewed under the new acreage cap, if prices for biofuel commodities rise high enough, a large amount of CRP land may be lost when owners decide not renew, but to seek “greener pastures” in switchgrass or corn production for biofuel.  A mass exodus of from the CRP program would be a disaster for conservation of grassland species in North America.  In addition, there is the possibility that the USDA could change the rules for CRP contracts at some point in the future to allow switchgrass production on CRP lands.

Over at the Biofuels and Bio-based Carbon Mitigation Blog of the School of Natural Resources and Environment at the University of Michigan, Kristen Johnson wrote a great post discussing the potential magnitude of the conversion of CRP lands to switchgrass production for cellulosic biofuel.  She states that acres currently in corn are unlikely to be converted to switchgrass, since EPA guidelines call for a continued increase in corn-based ethanol production in the near future.

As long as the prices of other commodities like soybeans are high, that leaves only pastureland, hay production land, and CRP land as prime targets for conversion to biofuels.  Compared to cropland, these land uses are all of much higher value to wildlife.

The take-home message here is this: if you value grassland habitats and the wildlife that depends on them, keep an eye on this issue.  While the Union of Concerned Scientists letter doesn’t specifically address habitat loss, it does shed light on the emissions consequences of biofuel production, and is a step toward helping our public agencies recognize that biofuels are not free of collateral damage.  You can view the letter at the Union of Concerned Scientists “Take Action” site.