Invasive Species – How Do They Impact Threatened and Endangered Species?
By Ellen Jacquart
There is wide acceptance that invasive species impact threatened and endangered species, but there is surprisingly little research on this topic in Indiana. Despite this lack of research, there are several examples of rare species that are being impacted by invasive species in Indiana.
White-nose syndrome on Indiana bat – Indiana bat (Myotis sodalis) is a federally endangered bat that hibernates in large clusters in caves every winter. Its population has been declining for the last several decades; though the reasons are not clear, it may be a combination of human disturbance, cave commercialization and improper cave gating, summer habitat loss and pesticides. Despite the overall decrease in the species’ number, Indiana’s populations have remained steady or increased over time. However, the recent introduction of white-nose syndrome (WNS) puts Indiana’s bats at further risk. WNS is an infectious disease associated with a fungus (Geomyces destructans) believed to have been introduced from Europe. WNS is responsible for unprecedented levels of mortality among hibernating bats in North America and is named for the white fungal growth that invades the skin tissue on the muzzle, wings and ears of cave-dwelling bats during winter hibernation. The 2013 population surveys of Indiana bat in Indiana found a 16% decline in the three years since WNS was found in Indiana, and further reductions in population are expected over time. Overall, the disease has caused the death of an estimated 5.7 – 6.7 million bats across eastern North America with estimates of mortality often exceeding 90% in caves that have experienced multiple years of infection.
Crown vetch on Short’s goldenrod – Short’s goldenrod (Solidago shortii) is known from just two places in the world, one of which is in Indiana along the Blue River. This bright yellow-flowered goldenrod grows from the cracks of limestone that line the river banks. Being a fairly severe habitat, there are few native plants that compete with it in such a location. Unfortunately, crown vetch (Securigera varia), an aggressive legume used for erosion control, has found its way to these riverine habitats. Crown vetch grows quickly and spreads through rhizomes, and is able to invade these limestone cracks, directly competing with the Short’s goldenrod.
Phragmites on pipewort - Pipewort (Eriocaulon aquaticum) is a tiny state-endangered plant that grows along lake shores in northern Indiana. A cap of white flowers tops a flower stalk less than six inches tall. Habitat loss through lake development and shoreline destruction is the primary reason for its rarity, but invasive species are also taking a toll. Pipewort has no chance when phragmites (Phragmites australis ssp. australis) invades a lakeshore, as this invasive grass can reach 20’ tall and forms a dense monoculture that eliminates pipewort and all other plants.
Phragmites on spotted turtle – Spotted turtle (Clemmys guttata) is a small turtle with a dark shell peppered with yellow dots. This state-endangered turtle is found in fens and wet prairies in northern Indiana and eats slugs, worms, snails, and spiders. At the end of breeding season, the female turtles find an open area to dig a nest and lay 3-4 eggs. The nest site is carefully chosen to provide adequate solar heat for developing eggs, as nest temperature is the most important factor for embryo development and actually determines the sex of the embryos. Phragmites australis ssp. australis also prefers to grow in open areas, and often invades the kind of habitats in which turtles are most likely to nest. The tall, dense monoculture of phragmites near turtle nests alters the microenvironment of turtle nests during incubation, particularly the nest temperature, threatening successful reproduction of the turtles.
Ellen Jacquart is the Director of Northern Indiana Stewardship for the Nature Conservancy in Indiana. She has worked in Indiana’s natural areas since 1987.