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Nature of Suit Code: 893
Nature of Suit: Environmental Matters
Cause of Action: 

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populations may harbor important adaptive genetic variation (Scudder 1989, Guo et al. 2005, 

Lesica and Allendorf 1995). 

Geographical isolation from core populations may influence peripheral populations in other 

ways. Studies of numerous species have shown that range collapse frequently originates in the 

core or area of high abundance, contracting to remaining peripheral populations (Lomolino and 

Channell 1995, Channell and Lomolino 2000a, Rodriguez 2002). This pattern appears to result 

from anthropogenic threats (e.g., habitat loss, exotic species invasion) that overwhelm normal 

species abundance patterns (Channell and Lomolino 2000a, 2000b). These threats often spread 

across the landscape like a contagion, with those populations that are exposed last persisting the 

longest (Channell and Lomolino 2000b). Peripheral populations may be sufficiently isolated 

from the threats affecting the species’ core that the populations are buffered from negative 

impacts (Araujo and Williams 2001). Therefore, the edge of a species range may provide 

important refugia for rare or imperiled species (Lomolino and Channell 1995). 

As previously discussed, peripheral populations may occupy atypical or less favorable habitats 

(Lomolino and Channell 1995, Channel and Lomolino 2000a, 2000b). To persist, these 

individuals must adapt to different and possibly more extreme environmental factors and 

selective forces. Additionally, peripheral populations may be genetically and ecologically 

different from other peripheral populations and the core populations (Lomolino and Channell 

1995). Further, peripheral populations may be better adapted to long-term rangewide 

environmental changes, such as global climate change (Hunter 1991, Araujo and Williams 

2001). These individuals may be best adapted to establishing themselves in the shifting habitats 

created by changing climate (Fraser 2000). 

Thus, both core and peripheral populations make contributions to a species’ persistence due to 

their different characteristics. Because of the relationship that exists among core and peripheral 

populations within a species’ range, conservation and management of both should be considered 

equally important (Brown 1984, Pulliam 1988, Furlow and Armijo-Prewitt 1995, Lesica and 

Allendorf 1995, Lomolino and Channell 1997). 

Justification for Recovery Units

Research on core and peripheral populations and the importance of population representation in 

species conservation suggest that maintaining the current distribution avoids extinction and 

ensures long-term survival (Furlow and Armijo-Prewitt 1995, Lesica and Allendorf 1995, 

Channell and Lomolino 2000a, Shaffer and Stein 2000). Humphrey (1992) proposed that 

Indiana bats are separated into interbreeding populations and that management programs should 

be developed according to these delimitations (Humphrey 1992). Recovery Units are a tool 

developed to maintain the distribution of wide-ranging species that have multiple populations or 

varying ecological pressures in different parts of the range (National Marine Fisheries Service 

2004). Recovery Units are geographically or otherwise identifiable and are essential to conserve 

genetic robustness, demographic robustness, or other necessary biological features. Recovery 

Units may not be reclassified or delisted separately. 

As proposed in this Plan, Recovery Units protect both core and peripheral populations. 

Furthermore, Recovery Units address the principle of representation by aiding conservation of 

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natural variation across populations. As discussed in the Population Distribution and Abundance 

section of this plan, preliminary evidence suggests that the Northeast populations of the species 

have different levels of genetic diversity than the rest of the Indiana bat population and also are 

of more recent origin; additionally, data from two hibernacula in the Appalachian region also 

suggest recent divergence and isolation (M. Vonhof, pers.comm., 2006). Research is needed to 

confirm this pattern and to further explore possible genetic variation across the species range. 

Such variation is possible given suggestions of population discreteness from banding return data 

(Hall 1962, Barbour and Davis 1969, Gardner and Cook 2002). Variation in habitat and 

environmental conditions between core and peripheral populations of the species may also have 

resulted in differences in adaptive capabilities (Lomolino and Channell 1995, Channel and 

Lomolino 2000a, 2000b). Protecting populations across the species’ range ensures preservation 

of these adaptive capabilities. 

Recovery Units also allow for adherence to the tenets of redundancy and resiliency. Population 

redundancy is addressed in this plan by protecting 80 percent of the Priority 1 hibernacula and 50 

percent of the Priority 2 hibernacula in each Recovery Unit (see Reclassification Criterion 1 and 

Delisting Criterion 1). The principle of redundancy is also addressed by requiring that Indiana 

bat population levels in each Recovery Unit have a positive population growth rate over five 

survey periods (see Reclassification Criterion 3 and Delisting Criterion 3). Tracking measures of 

population redundancy and resiliency will also be helpful in monitoring the population in the 

Ozark-Central region, where the population has declined significantly since 1990 (see Figure 7 

and Population Trends in Hibernacula section of this plan). 

We are unable to assess—and thus address— population resiliency at this time because the 

characteristics of a viable population or maternity colony are not known. However, research 

actions described within this Recovery Plan will produce results that will facilitate this endeavor. 

Delineation of Recovery Units

As alluded to above, the delineation of Recovery Units relies on a combination of preliminary 

evidence of population discreteness and genetic differentiation, differences in population trends, 

and broad-level differences in macrohabitats and land use. When Recovery Unit delimitations 

suggested by these factors were geographically close to state boundaries, the Recovery Unit 

borders were shifted to match the state boundaries in order to facilitate future conservation and 

management. This draft revised plan proposes four Recovery Units for the species: OzarkCentral, Midwest, Appalachian Mountains, and Northeast (Figure 14). The proposed 

delineations will be revised as additional information becomes available from research outlined 

in the Recovery Actions portion of this document. 

Banding returns suggest the Indiana bat population is not panmictic (Hall 1962, Barbour and 

Davis 1969, Gardner and Cook 2002). Banding data by Hall (1962) showed that individuals 

hibernating in Kentucky migrated north to Indiana and western Ohio during the summer. 

Barbour and Davis (1969) determined that female bats and most male bats banded in Kentucky 

migrate north in the spring to Indiana, western Ohio, and southern Michigan. Gardner and Cook 

(2002) summarized banding returns reported in Kurta 1980, LaVal and LaVal 1980, Bowles 

1981, Walley 1981, and Kurta and Murray 2002. Mature female bats from hibernacula in 

Kentucky and Indiana summered in western Ohio, Indiana, and Michigan (Gardner and Cook 

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