D. Culver | American University (original) (raw)
Papers by D. Culver
Springs are interfaces between groundwater and surface habitats and may play an important role in... more Springs are interfaces between groundwater and surface habitats and may play an important role in the study of subterranean animals. In this systematic evidence review and meta-analysis, we explore whether observations of stygobionts in springs are relevant and more common than observations of epigean animals in groundwater. We searched the Web of Science database for papers on groundwater fauna and spring fauna. For each paper we found, we recorded whether the paper reported the occurrence of typical stygobionts in springs, of surface animals in groundwater, or of the same taxa in both habitats. If so, we recorded how many such species were reported. We also recorded the scientific discipline of each study and the year of publication. Our search yielded 342 papers. A considerable number of these papers reported stygobionts in springs: 20% of papers dealing with groundwater fauna and 16% of papers dealing with spring fauna reported the occurrence of stygobionts in spring habitats. Both the number of papers that mentioned stygobionts in springs, and the number of stygobiont species that were documented in springs, were higher than equivalent measures for the occurrence of surface fauna underground. We also detected a positive relationship between year of publication and the number of reports of stygofauna in springs. To broaden the insights from biological research on underground environments, we suggest that springs should be considered not only as simple sampling points of stygobionts but also as core stygobiont habitats.
Recent interdisciplinary research in a shallow valley-floor cave in southwestern Virginia shows t... more Recent interdisciplinary research in a shallow valley-floor cave in southwestern Virginia shows that hydrologic, geochemical and biological data can be integrated to improve characterization of epikarst hydrologic properties. Three in-cave sites (two< 20m and one< ...
The American Midland Naturalist, 2006
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting... more BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.
International Journal of Speleology, 2013
The epikarst habitat Wherever there is soil covering base rock, there is a zone of contact betwee... more The epikarst habitat Wherever there is soil covering base rock, there is a zone of contact between the rock and the soil, typically consisting of an unconsolidated layer of rock mixed with soil-the regolith. This zone often has spaces larger than the soil above. When the base rock is water soluble at the pH of water in the area, these spaces are greatly enhanced by the dissolution of rock into small channels and cavities. It is the shallow part of karst areas, where stress release, climate, tree roots, and karst processes fracture and enlarge rock joints and cracks, creating a more permeable and porous zone over the carbonate rock in which only a few vertical joints and cracks occur (Bakalowicz, 2012).
International Journal of Speleology, 2013
The epikarst habitat Wherever there is soil covering base rock, there is a zone of contact betwee... more The epikarst habitat Wherever there is soil covering base rock, there is a zone of contact between the rock and the soil, typically consisting of an unconsolidated layer of rock mixed with soil-the regolith. This zone often has spaces larger than the soil above. When the base rock is water soluble at the pH of water in the area, these spaces are greatly enhanced by the dissolution of rock into small channels and cavities. It is the shallow part of karst areas, where stress release, climate, tree roots, and karst processes fracture and enlarge rock joints and cracks, creating a more permeable and porous zone over the carbonate rock in which only a few vertical joints and cracks occur (Bakalowicz, 2012).
First, we would first like to thank Professor Curl for his comments and interest in our recent wo... more First, we would first like to thank Professor Curl for his comments and interest in our recent work on the geographic distributions of caves and subterranean fauna in the coterminous United States (Culver et al. 1999). We welcome the opportunity to discuss and clar-ify some of the statements made in our manuscript. Each comment of Professor Curl's is addressed in turn. We wish to emphasize that any statistical analysis presented in the paper was solely exploratory in nature in order to provide some initial confirma-tion for the conclusion of similar spatial distributions for the caves and cave species (Figs. 1 & 2). 1) We did not test whether the relationship between S (number of species) and C (number of caves) was linear for two reasons. a) The emphasis in this paper was on demonstrating graphically that a relationship (linear or otherwise) exists between S and C. That can be seen quite clearly in figure 3, which also shows that for large numbers of caves the relationship is a...
Trends and Global Prospects, 2008
This chapter presents a brief overview of subterranean aquatic systems, with emphasis on three to... more This chapter presents a brief overview of subterranean aquatic systems, with emphasis on three topics: (1) present-day negative human impacts on the subterranean hydrosphere; (2) policy/management measures that integrate socioeconomic and ecological arguments; ...
Proceedings of the National Academy of Sciences, 1971
A model is developed for the coexistence and exclusion of species over a region of similar habita... more A model is developed for the coexistence and exclusion of species over a region of similar habitable patches. Since the balance of local extinction and colonization would leave some patches unoccupied even without competitors, species may coexist even when all the patches are the same. Regional competition coefficients are found when species affect the local extinction or migration rates of each other. Rare species can regulate each other and even exclude other species completely.
Acta Carsologica, 2012
Tvorijo jih šibki podzemeljski vodni tokovi tik pod površjem, običajno do globine enega metra. Za... more Tvorijo jih šibki podzemeljski vodni tokovi tik pod površjem, običajno do globine enega metra. Za trajno mokra mesta je značilno počrnelo listje v manjših talnih vdolbinah. V sušnih obdobjih lahko tanek tok vode preneha, vendar se voda zadržuje nad glinenim dnom močila. Te vode primezijo na površje v drobnih izvirih; od tod slovensko ime mezišča za te habitate. Stik s talno vodo razmejuje mezišča od drugih majhnih vodnih teles, t. i., močil, ki lahko nastanejo tudi na druge načine. Običajno so za favno mezišč značilne vrste, ki so prilagojene na življenje v podzemeljskih habitatih in so praviloma brez oči ali pigmenta. V članku so opisane osnovne kemijske in hidrološke značilnosti mezišč ter navedeni osnovni predstavniki njihove favne. Habitati so predstavljeni nekoliko širše s pregledom možnosti njihove poselitve, morfoloških značilnosti vrst ter možnih povezav z globljimi podzemelj skimi habitati.
Journal of Natural History, 2010
Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf ... more Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Journal of Crustacean Biology, 2010
The amphipod genus Stygobromus occurs in a variety of subterranean habitats in North America, inc... more The amphipod genus Stygobromus occurs in a variety of subterranean habitats in North America, including caves, phreatic (groundwater) lakes, and superficial subterranean habitats (seeps and epikarst). The habitats share the absence of light but differ in other features, such as pore size of the habitat, available food, and degree of seasonality. Measurements of body size, antennal size, and antennal segment number of type specimens were compared for 56 species occurring in the eastern United States. Except for differences in body size, differences among species in the four different habitats were not significant. Body size was related to relative pore size of the habitat, e.g., epikarst, with the smallest spaces, had the smallest species. However, in all habitats, there was one very large species (. 15mm); these enigmatic species apparently occupy a distinct ecological niche, perhaps being more predatory. Differences in relative antennal size showed no significant differences among habitats, and differences in number of antennal segments were marginally significant (P 5 0.06) among habitat types and not in the predicted pattern. Differences among habitats in seasonality and available food seemed to be a minor part of the selective environment; absence of light seemed to be a major part of the selective environment.
Journal of Biogeography, 1987
Journal of Biogeography, 2005
... Christman, MC, Culver, DC, Madden, MK and White, D. (2005), Patterns of endemism of the easte... more ... Christman, MC, Culver, DC, Madden, MK and White, D. (2005), Patterns of endemism of the eastern North American cave fauna. ... Valentine is in a unique genus of trechine (carabid) beetles and is known from a single cave in Greenbrier County, West Virginia (Valentine, 1932). ...
Hydrogeology Journal, 2007
The distribution of 27 copepod species was determined in 35 drips in four Slovenian caves (Dimnic... more The distribution of 27 copepod species was determined in 35 drips in four Slovenian caves (Dimnice, Postojna Planina Cave System, Škocjanske Jame, Županova Jama), and of ten species from 13 drips in one US cave (Organ Cave, West Virginia). The dripping water comes from epikarst, the skin of karst. A significant fraction of the copepod species found (nine species in Slovenia and three in West Virginia) occurred over a maximum linear extent of 100 m. These and other localized distributions probably resulted from colonization of epikarst by an ancestral surface population in a single location, with subsequent lateral spread in the direction of epikarst flow. This suggests that the distribution of copepods could potentially be used to trace major flow paths in epikarst without the need for the injection of dyes or other tracers.
Evolution, 1968
... Coryell 1 14 0 6 9 1 Bell 1 5 0 7 1 0 Burnett 1 21 3 15 7 1 Edwards N. 7 5 4 13 5 0 Edwards S... more ... Coryell 1 14 0 6 9 1 Bell 1 5 0 7 1 0 Burnett 1 21 3 15 7 1 Edwards N. 7 5 4 13 5 0 Edwards SW 5 2 0 1 6 4 Val Verde 1 7 0 4 7 1 Kerr 2 8 0 11 3 0 Real 0 5 0 0 4 2 ... Frio 1 5 2 2 2 0 Uvalde 6 2 1 3 1 0 Edwards 10 0 1 6 2 0 Val Verde 0 6 0 6 0 0 Terrell 9 2 0 5 3 0 Sutton 1 2 0 3 0 0 ...
Evolution, 1997
... The data are part of a study on heritability and genetic correlations among G. minus pop-ulat... more ... The data are part of a study on heritability and genetic correlations among G. minus pop-ulations (Fong 1989, Jernigan et al. 1994). ... A geographically and hydrologically distant spring population, Bone Norman Re-surgence, was used as the outgroup. ...
Conservation Biology, 2000
We assembled a list of obligate cave-dwelling species and subspecies, their county distribution, ... more We assembled a list of obligate cave-dwelling species and subspecies, their county distribution, and their provisional global conservation rank. A total of 927 species and 46 additional subspecies in 96 families exclusively from cave and associated subterranean habitats have been described in the 48 contiguous states of the United States. The terrestrial (troglobitic) species are concentrated in northeast Alabama (especially Jackson County), with other concentrations in Kentucky, Texas, Virginia, and West Virginia. Only 23 counties, comprising less than 1% of the land area of the 48 contiguous states, account for over 50% of the terrestrial species and subspecies. The aquatic (stygobitic) species are concentrated in Hays County, Texas, with other concentrations in Florida, Oklahoma, Texas, Virginia, and West Virginia. Only 18 counties, comprising less than 1% of the land area, account for over 50% of the aquatic species and subspecies. Endemism is high, with 54% of the species known from a single county. Approximately 95% of the species are listed by The Nature Conservancy as vulnerable or imperiled in the United States. These cave species comprise 50% of all vulnerable or imperiled species listed in databases of the Natural Heritage Program. Less than 4% of these subterranean species have federal status. Conservation can best be accomplished through habitat protection, which must include protection of the associated surface habitat. Fauna Cavernícola Obligada de los 48 Estados Contiguos de E.U.A.
Biological Journal of the Linnean Society, 1994
ABSTRACT The shape of the fitness function was investigated in a spring population (Davis Spring)... more ABSTRACT The shape of the fitness function was investigated in a spring population (Davis Spring) and a cave population (Organ Cave) of the amphipod Gammarus minus in southern West Virginia. The first three principal components of a series of size, antennal and eye measurements and two fitness components (amplexus and number of eggs) were investigated. Smoothing splines using generalized cross-validation scores were found as were least-squares quadratic regression equations. Confidence intervals on shape, as determined by a smoothing parameter, were calculated using a bootstrap approach. Out of 18 cases, there were six cases of no selection, six cases of directional (monotonic) selection, one case of stabilizing selection, one case of disruptive selection, and four cases of selection with multiple internal maxima and minima. Selection on the cave population was frequently directional (5), resulting from strong directional selection for increased size, larger antennae, and smaller eyes. Selection on the spring population, the ancestral habitat for the species, was frequently non-monotonic (five cases) and rarely directional (one case). In both populations, stabilizing selection was rare and no more common than disruptive selection.
Springs are interfaces between groundwater and surface habitats and may play an important role in... more Springs are interfaces between groundwater and surface habitats and may play an important role in the study of subterranean animals. In this systematic evidence review and meta-analysis, we explore whether observations of stygobionts in springs are relevant and more common than observations of epigean animals in groundwater. We searched the Web of Science database for papers on groundwater fauna and spring fauna. For each paper we found, we recorded whether the paper reported the occurrence of typical stygobionts in springs, of surface animals in groundwater, or of the same taxa in both habitats. If so, we recorded how many such species were reported. We also recorded the scientific discipline of each study and the year of publication. Our search yielded 342 papers. A considerable number of these papers reported stygobionts in springs: 20% of papers dealing with groundwater fauna and 16% of papers dealing with spring fauna reported the occurrence of stygobionts in spring habitats. Both the number of papers that mentioned stygobionts in springs, and the number of stygobiont species that were documented in springs, were higher than equivalent measures for the occurrence of surface fauna underground. We also detected a positive relationship between year of publication and the number of reports of stygofauna in springs. To broaden the insights from biological research on underground environments, we suggest that springs should be considered not only as simple sampling points of stygobionts but also as core stygobiont habitats.
Recent interdisciplinary research in a shallow valley-floor cave in southwestern Virginia shows t... more Recent interdisciplinary research in a shallow valley-floor cave in southwestern Virginia shows that hydrologic, geochemical and biological data can be integrated to improve characterization of epikarst hydrologic properties. Three in-cave sites (two< 20m and one< ...
The American Midland Naturalist, 2006
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting... more BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.
International Journal of Speleology, 2013
The epikarst habitat Wherever there is soil covering base rock, there is a zone of contact betwee... more The epikarst habitat Wherever there is soil covering base rock, there is a zone of contact between the rock and the soil, typically consisting of an unconsolidated layer of rock mixed with soil-the regolith. This zone often has spaces larger than the soil above. When the base rock is water soluble at the pH of water in the area, these spaces are greatly enhanced by the dissolution of rock into small channels and cavities. It is the shallow part of karst areas, where stress release, climate, tree roots, and karst processes fracture and enlarge rock joints and cracks, creating a more permeable and porous zone over the carbonate rock in which only a few vertical joints and cracks occur (Bakalowicz, 2012).
International Journal of Speleology, 2013
The epikarst habitat Wherever there is soil covering base rock, there is a zone of contact betwee... more The epikarst habitat Wherever there is soil covering base rock, there is a zone of contact between the rock and the soil, typically consisting of an unconsolidated layer of rock mixed with soil-the regolith. This zone often has spaces larger than the soil above. When the base rock is water soluble at the pH of water in the area, these spaces are greatly enhanced by the dissolution of rock into small channels and cavities. It is the shallow part of karst areas, where stress release, climate, tree roots, and karst processes fracture and enlarge rock joints and cracks, creating a more permeable and porous zone over the carbonate rock in which only a few vertical joints and cracks occur (Bakalowicz, 2012).
First, we would first like to thank Professor Curl for his comments and interest in our recent wo... more First, we would first like to thank Professor Curl for his comments and interest in our recent work on the geographic distributions of caves and subterranean fauna in the coterminous United States (Culver et al. 1999). We welcome the opportunity to discuss and clar-ify some of the statements made in our manuscript. Each comment of Professor Curl's is addressed in turn. We wish to emphasize that any statistical analysis presented in the paper was solely exploratory in nature in order to provide some initial confirma-tion for the conclusion of similar spatial distributions for the caves and cave species (Figs. 1 & 2). 1) We did not test whether the relationship between S (number of species) and C (number of caves) was linear for two reasons. a) The emphasis in this paper was on demonstrating graphically that a relationship (linear or otherwise) exists between S and C. That can be seen quite clearly in figure 3, which also shows that for large numbers of caves the relationship is a...
Trends and Global Prospects, 2008
This chapter presents a brief overview of subterranean aquatic systems, with emphasis on three to... more This chapter presents a brief overview of subterranean aquatic systems, with emphasis on three topics: (1) present-day negative human impacts on the subterranean hydrosphere; (2) policy/management measures that integrate socioeconomic and ecological arguments; ...
Proceedings of the National Academy of Sciences, 1971
A model is developed for the coexistence and exclusion of species over a region of similar habita... more A model is developed for the coexistence and exclusion of species over a region of similar habitable patches. Since the balance of local extinction and colonization would leave some patches unoccupied even without competitors, species may coexist even when all the patches are the same. Regional competition coefficients are found when species affect the local extinction or migration rates of each other. Rare species can regulate each other and even exclude other species completely.
Acta Carsologica, 2012
Tvorijo jih šibki podzemeljski vodni tokovi tik pod površjem, običajno do globine enega metra. Za... more Tvorijo jih šibki podzemeljski vodni tokovi tik pod površjem, običajno do globine enega metra. Za trajno mokra mesta je značilno počrnelo listje v manjših talnih vdolbinah. V sušnih obdobjih lahko tanek tok vode preneha, vendar se voda zadržuje nad glinenim dnom močila. Te vode primezijo na površje v drobnih izvirih; od tod slovensko ime mezišča za te habitate. Stik s talno vodo razmejuje mezišča od drugih majhnih vodnih teles, t. i., močil, ki lahko nastanejo tudi na druge načine. Običajno so za favno mezišč značilne vrste, ki so prilagojene na življenje v podzemeljskih habitatih in so praviloma brez oči ali pigmenta. V članku so opisane osnovne kemijske in hidrološke značilnosti mezišč ter navedeni osnovni predstavniki njihove favne. Habitati so predstavljeni nekoliko širše s pregledom možnosti njihove poselitve, morfoloških značilnosti vrst ter možnih povezav z globljimi podzemelj skimi habitati.
Journal of Natural History, 2010
Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf ... more Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Journal of Crustacean Biology, 2010
The amphipod genus Stygobromus occurs in a variety of subterranean habitats in North America, inc... more The amphipod genus Stygobromus occurs in a variety of subterranean habitats in North America, including caves, phreatic (groundwater) lakes, and superficial subterranean habitats (seeps and epikarst). The habitats share the absence of light but differ in other features, such as pore size of the habitat, available food, and degree of seasonality. Measurements of body size, antennal size, and antennal segment number of type specimens were compared for 56 species occurring in the eastern United States. Except for differences in body size, differences among species in the four different habitats were not significant. Body size was related to relative pore size of the habitat, e.g., epikarst, with the smallest spaces, had the smallest species. However, in all habitats, there was one very large species (. 15mm); these enigmatic species apparently occupy a distinct ecological niche, perhaps being more predatory. Differences in relative antennal size showed no significant differences among habitats, and differences in number of antennal segments were marginally significant (P 5 0.06) among habitat types and not in the predicted pattern. Differences among habitats in seasonality and available food seemed to be a minor part of the selective environment; absence of light seemed to be a major part of the selective environment.
Journal of Biogeography, 1987
Journal of Biogeography, 2005
... Christman, MC, Culver, DC, Madden, MK and White, D. (2005), Patterns of endemism of the easte... more ... Christman, MC, Culver, DC, Madden, MK and White, D. (2005), Patterns of endemism of the eastern North American cave fauna. ... Valentine is in a unique genus of trechine (carabid) beetles and is known from a single cave in Greenbrier County, West Virginia (Valentine, 1932). ...
Hydrogeology Journal, 2007
The distribution of 27 copepod species was determined in 35 drips in four Slovenian caves (Dimnic... more The distribution of 27 copepod species was determined in 35 drips in four Slovenian caves (Dimnice, Postojna Planina Cave System, Škocjanske Jame, Županova Jama), and of ten species from 13 drips in one US cave (Organ Cave, West Virginia). The dripping water comes from epikarst, the skin of karst. A significant fraction of the copepod species found (nine species in Slovenia and three in West Virginia) occurred over a maximum linear extent of 100 m. These and other localized distributions probably resulted from colonization of epikarst by an ancestral surface population in a single location, with subsequent lateral spread in the direction of epikarst flow. This suggests that the distribution of copepods could potentially be used to trace major flow paths in epikarst without the need for the injection of dyes or other tracers.
Evolution, 1968
... Coryell 1 14 0 6 9 1 Bell 1 5 0 7 1 0 Burnett 1 21 3 15 7 1 Edwards N. 7 5 4 13 5 0 Edwards S... more ... Coryell 1 14 0 6 9 1 Bell 1 5 0 7 1 0 Burnett 1 21 3 15 7 1 Edwards N. 7 5 4 13 5 0 Edwards SW 5 2 0 1 6 4 Val Verde 1 7 0 4 7 1 Kerr 2 8 0 11 3 0 Real 0 5 0 0 4 2 ... Frio 1 5 2 2 2 0 Uvalde 6 2 1 3 1 0 Edwards 10 0 1 6 2 0 Val Verde 0 6 0 6 0 0 Terrell 9 2 0 5 3 0 Sutton 1 2 0 3 0 0 ...
Evolution, 1997
... The data are part of a study on heritability and genetic correlations among G. minus pop-ulat... more ... The data are part of a study on heritability and genetic correlations among G. minus pop-ulations (Fong 1989, Jernigan et al. 1994). ... A geographically and hydrologically distant spring population, Bone Norman Re-surgence, was used as the outgroup. ...
Conservation Biology, 2000
We assembled a list of obligate cave-dwelling species and subspecies, their county distribution, ... more We assembled a list of obligate cave-dwelling species and subspecies, their county distribution, and their provisional global conservation rank. A total of 927 species and 46 additional subspecies in 96 families exclusively from cave and associated subterranean habitats have been described in the 48 contiguous states of the United States. The terrestrial (troglobitic) species are concentrated in northeast Alabama (especially Jackson County), with other concentrations in Kentucky, Texas, Virginia, and West Virginia. Only 23 counties, comprising less than 1% of the land area of the 48 contiguous states, account for over 50% of the terrestrial species and subspecies. The aquatic (stygobitic) species are concentrated in Hays County, Texas, with other concentrations in Florida, Oklahoma, Texas, Virginia, and West Virginia. Only 18 counties, comprising less than 1% of the land area, account for over 50% of the aquatic species and subspecies. Endemism is high, with 54% of the species known from a single county. Approximately 95% of the species are listed by The Nature Conservancy as vulnerable or imperiled in the United States. These cave species comprise 50% of all vulnerable or imperiled species listed in databases of the Natural Heritage Program. Less than 4% of these subterranean species have federal status. Conservation can best be accomplished through habitat protection, which must include protection of the associated surface habitat. Fauna Cavernícola Obligada de los 48 Estados Contiguos de E.U.A.
Biological Journal of the Linnean Society, 1994
ABSTRACT The shape of the fitness function was investigated in a spring population (Davis Spring)... more ABSTRACT The shape of the fitness function was investigated in a spring population (Davis Spring) and a cave population (Organ Cave) of the amphipod Gammarus minus in southern West Virginia. The first three principal components of a series of size, antennal and eye measurements and two fitness components (amplexus and number of eggs) were investigated. Smoothing splines using generalized cross-validation scores were found as were least-squares quadratic regression equations. Confidence intervals on shape, as determined by a smoothing parameter, were calculated using a bootstrap approach. Out of 18 cases, there were six cases of no selection, six cases of directional (monotonic) selection, one case of stabilizing selection, one case of disruptive selection, and four cases of selection with multiple internal maxima and minima. Selection on the cave population was frequently directional (5), resulting from strong directional selection for increased size, larger antennae, and smaller eyes. Selection on the spring population, the ancestral habitat for the species, was frequently non-monotonic (five cases) and rarely directional (one case). In both populations, stabilizing selection was rare and no more common than disruptive selection.