Invasive species are known to be one of the major contributors to amphibian declines across the globe. Such was the case for the endangered the Sierra Nevada yellow-legged frog (Rana sierrae) in Yosemite National Park. In the early 1900s, stocks of nonnative fish, mainly predatory trout species (Oncorhynchus sp. and Salvelinus sp.), were introduced into naturally fishless habitats. Stocking fish, along with disease, likely led to a massive decline in yellow-legged frog populations. However, with the help of restoration efforts, including cessation of stocking nonnative fish, this story has a happy ending. A recent study published in PNAS by Knapp et al. (2016) found that the frog’s abundance has substantially increased over the past 20 years, suggesting that the effects invasive species have on natural populations may in fact be reversible. Article by Shelly Leachman for Science Daily.
Image courtesy of USGS (photographer: Devin Edmonds)
Vanessa Wuerthner, Ph.D. student in Biology
Invasive bush honeysuckles (Lonicera spp.) are changing the appearance of native birds. Yellow-shafted Northern Flickers have recently been found with reddish flight feathers. These abnormally colored birds are far from the range of western Red-shafted Flickers, which they are known to hybridize with and produce intermediately colored offspring. A recent study published by Hudon et al. in The Auk shows that the real culprit is the pigment rhodoxanthin, found in non-native honeysuckles. Berries of these plants have been known to cause color changes in other bird species such as the Cedar Waxwing and Yellow-breasted Chat. This has potentially detrimental effects on mate selection where color often serves as an indicator of fitness. Article by Douglas Maine in Newsweek
Sheila Moore, Master's student in Biology
Bad news for cat lovers everywhere… as they are being implicated in the extinction of dozens of species including rare birds, small mammals, and amphibians. A recent study by Loss et al. in Nature Communications has estimated that cats have killed somewhere between 1.3 and 4 billion birds, and 6.3 to 22.3 billion mammals every year. Island ecosystems are particularly vulnerable to feline predation. Since many of the species on islands have evolved in isolation away from mammal predators, many do not have the adequate defense mechanisms to evade domestic cats. One study has shown that cats are a threat to 8% of critically endangered island species around the world. It is not by random chance that cats have done exceptionally well in various habitats. Humans have transported cats and facilitated their spread all over the globe. Their high population growth can also be attributed to the supplemental food and resources they gain from living near or with humans. So what can be done to protect vulnerable species from cats? The idea of putting down huge numbers of cats is rarely appealing to the general public. Therefore, humans need to start acknowledging that if cats are going to be kept as pets, they should be treated like pets. This includes responsible pet ownership practices such as neutering and keeping them indoors. Article by Jacqueline Ronson in Inverse.
Susan Lee, Master’s Student in Biology
Entomologists around the world are saying in unison, “we told you so!" A recent study on the economic and financial impacts of invasive insect suggests that costs of these invasive pests come to around 69 billion euros’ worth of damage per year. That’s roughly 75 billion in US dollars. The results came from an extensive analysis of over 700 articles, books and associated literature, and all in all, they prove one thing: these pint-sized pests have a disproportionately large impact on both ecosystems and society. Some of the biggest offenders are often the least publicized; the voracious Formosan subterranean termite, the cabbage moth, and the spruce longhorn beetle each cause billions of euros/dollars worth of damage yearly. North America leads in terms of total financial loss at around 24.5 billion euros, with Europe showing a markedly lower loss at around 3.2 billion. It is important to note, though, that the authors suggest that this finding may come from a relative lack of documentation of economic losses in Europe. Health and agricultural industries are the hardest hit sectors, with insects consuming a whopping 40% of agricultural production worldwide, and billions of dollars’ worth in treatment and other costs associated invasive species. Article in Science Daily.
Isaiah Barker, Master's Student in Geography
In the fight against the invasive hemlock woolly adelgid (Adelges tsugae), one university is taking a stand. In 2009, Cornell University found the invasive insect in stretches of its 700-acre tree plantation. The insect attacks hemlock trees, feeding on sap, destroying pine needles, and typically results in mortality of infested trees. Because of this infestation, researchers at Cornell have begun to look for forms of biological control for the insect, such as introducing predators from their native range in Japan. With Cornell having one of the world’s leading agricultural and pest management departments, it has become clear that the hemlock woolly adelgid chose the wrong plantation to infest. Article by Max Carol in Treehugger.
Nick Buss, Ph.D. student in Biology
Sweden’s attempt to ban American lobsters in the EU has officially been denied in favor of pursuing ‘alternative measures.’ A small number of American lobsters captured in European waters sparked fears of eventual establishment and full-on invasion. Swedish scientists touted risks of the American species not only out-competing native lobsters but of breeding ultra-competitive hybrids that could one day overwhelm their entire range of habitats. This is a common thread in invasive species management, but in this case, it is not known if hybrids are even fertile let alone more fit than either contributing species. The other fear noted by the Swedish is the risk of American lobsters facilitating the invasion of American diseases that the European species would be undefended against. This would then further increase the invasion potential of the American lobster. This argument is refuted by American lobster researchers claiming that native populations are largely disease-free and thus are unlikely to bring diseases even in the worst-case scenario of an invasion. The block is being blamed on the power of the American lobster fishing industry which has been booming in response to recent environmental changes in the native range. Climate change has increased reproductive rates while overfishing of lobster predators has decreased their mortality rates, increasing populations and profitability. The battle is not yet over as we are yet to see what ‘alternative measures’ might be proposed and how each side may then respond. Article by Shawn Donnan in the Financial Times.
Shane Tripp, Graduate Student in Geography
And now featuring some of our research! Just out in Ecosphere, University of Florida PhD student, Patrick Milligan led a project examining the putative effects of an invasive ant on a key ecosystem function (decomposition) in an African savanna. The Big-headed ant (BHA), Pheidole megacephala, is one of the IUCN “world’s worst invaders” owing to its ability to form large “supercolonies” (expansive colonies) where introduced, its protein-loving tendencies, and its ability to recruit large numbers of ants to resources - including to my unattended tea snacks at the Mpala Research Station in Kenya. BHA is not only a nuisance to people, but it likely has large effects on ecosystems – it has been found to devastate arthropod communities. A recent invader to the Laikipia region in Kenya (a conservation hotspot due to its intact large animal community), we noticed that BHA heavily recruits to animal dung. The ants are likely capitalizing off of resources in dung. For the protein-loving ant this could mean arthropods that play functionally important roles in dung decomposition (beetles and termites). Pat collected a lot of cow dung and set up an experiment to test BHA impacts in the field. He put out dung pats and pitfall traps (cups in the ground) in locations invaded by BHA or not, and counted and identified dung associated arthropods. He found that while BHA reduced the abundance and diversity of arthropods, the functionally import guild of arthropods involved in decomposition were resilient to invasive ants. This paper nicely highlights that to uncover consequences of invaders, we need to go beyond assessing impacts on species diversity alone and also consider effects on functional guilds and the services they provide.
Kirsten Prior, Assistant Professor in Biology