Stable isotope and pen feeding trial studies confirm the value of horseshoe crab Limulus polyphemus eggs to spring migrant shorebirds in Delaware Bay. G. M. Haramis, W. A. Link, P. C. Osenton, D. B. Carter, R. G. Weber, N. A. Clark, M. A. Teece and D. S. Mizrahi. 2007. Journal of Avian Biology. 38: 367-376.
This study looked at Red Knots (Calidris canutus rufa) and Ruddy Turnstones (Arenaria interpres morinella)
during spring stopover in Delaware Bay. Stable isotope analysis was
able to discriminate between dietary items used by the free-ranging
birds, which relied heavily on horseshoe crab eggs. What I found most
interesting were the data on the birds in pens. Peak consumption rates
of crab eggs were around 20,000 eggs per bird per day. It was estimated
that it required about 5,000 eggs for knots to gain a gram of mass and
4,300 eggs for turnstones, indicating the large quantities of crab eggs
required for the maintenance of these shorebird populations during
stopover, and why it is critical to preserve and protect the crab spawning in the Bay.
Forest succession suppressed by an introduced plant-fungal symbiosis. J. A. Rudgers, J. Holah, S. P. Orr, and K. Clay. 2007. Ecology 88: 18-25.
Tall fescue (Lolium arundinaceum) is an introduced grass that now occupies greater than 15 million hectares in the eastern U.S. alone. About two-thirds of tall fescue is infected with a symbiotic fungus, Neotyphodium coenophialum. This paper looked at tree colonization and growth and plant species turnover in grasslands over a 12-year period; each had tall fescue, but only one had the fungus. There was a dramatic difference in the plots, with the fungus-infected plot having reduced tree establishment, tree growth, and plant species turnover. Part of the lack of colonization by trees was due in part that voles ate 65% more tree seedlings in infected plots than in plots without the fungus. The impact this introduced grass and its symbiont has on grassland-to-forest succession is profound. And since its outside of my area of expertise, it was really surprising to me.
The impact of climatic variation on the opportunity for sexual selection. S. D Twiss, C. Thomas, V. Poland, J. A. Graves, and P. Pomeroy. 2007. Biology Letters 3:12-15.
A study of gray seals (Halichoerus grypus) over nine years revealed that dominant males mated in wet years, whereas in years with less rainfall, subordinate males mate more. Females moved around more in dry years, so dominant males had access to only about half as many females, and far more subordinate males were able to mate. This study indicates that changes in local weather conditions alter the annual proportion of males contributing to the population -- and thus the gene pool -- by up to 61%. This has major implications for how populations of animals may be impacted by climate change by influencing which pass along their traits to the next generations. Hat tip.
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