Oliver R.W. Pergams

Evidence for a fundamental and pervasive shift away from nature-based recreation

After 50 years of steady increase, per capita visits to U.S. National Parks have declined since 1987. To evaluate whether we are seeing a fundamental shift away from peoples interest in nature, we tested for similar longitudinal declines in 16 time series representing four classes of nature participation variables: (i) visitation to various types of public lands in the U.S. and National Parks in Japan and Spain, (ii) number of various types of U.S. game licenses issued, (iii) indicators of time spent camping, and (iv) indicators of time spent backpacking or hiking. The four variables with the greatest per capita participation were visits to Japanese National Parks, U.S. State Parks, U.S. National Parks, and U.S. National Forests, with an average individual participating 0.74–2.75 times per year. All four time series are in downtrends, with linear regressions showing ongoing losses of −1.0% to −3.1% per year. The longest and most complete time series tested suggest that typical declines in per capita nature recreation began between 1981 and 1991, are proceeding at rates of −1.0% to −1.3% per year, and total to date −18% to −25%. Spearman correlation analyses were performed on untransformed time series and on transformed percentage year-to-year changes. Results showed very highly significant correlations between many of the highest per capita participation variables in both untransformed and in difference models, further corroborating the general downtrend in nature recreation. In conclusion, all major lines of evidence point to an ongoing and fundamental shift away from nature-based recreation.

Evolutionarily enlightened management

Here we review growing evidence that microevolutionary changes may often be rapid and, in many cases, occur on time frames comparable to human disturbance and anthropogenic change. Contemporary evolutionary change has been documented in relatively pristine habitats, in disturbed populations, under captive management, and in association with both intentional and inadvertent introductions. We argue that evolutionary thinking is thus relevant to conservation biology and resource management but has received insufficient consideration. Ignoring evolution may have a variety of consequences, including unpredicted evolutionary responses to disturbance and naive or inappropriate management decisions. Philosophically, we must also grapple with the issue of whether the evolution of adaptations to disturbance and degraded habitats is sometimes beneficial or something to be rigorously avoided. We advocate promoting evolutionarily enlightened management [Lecture Notes in Biomathematics 99 (1994) 248], in which both the ecological and evolutionary consequences of resource management decisions are considered.

Microevolution in island rodents.

We perform a meta-analysis on morphological data from four island rodent populations exhibiting microevolution (>≈ 100 years). Data consisting of incidences of skeletal variants, cranial, and external measurements are from house mice (Mus musculus) on one Welsh and one Scottish island, black rats (Rattus rattus) on two Galapagos islands, and deer mice (Peromyscus maniculatus) on three California Channel islands. We report extremely high rates of microevolution for many traits; 60% of all mensural traits measured changed at a rate of 600 d or greater (max. 2682 d). The proportion of all mensural traits evolving at 600–800 d (23%) was idiosyncratic and departed from an expected negative exponential distribution. We argue that selection, rather than founder events, is largely responsible for the substantial shifts in morphology seen among insular rodents. Examining individual traits, there is a trend towards the nose becoming longer and wider, while the skull becomes shallower, shown by both rats and mice on five different islands. We found a significant correlation between island size and degree of skeletal variant evolution and between island distance from the mainland (or nearest island) and degree of cranial and external character evolution. Thus, microevolution of rodents is greater on smaller and more remote islands.

RAPID MORPHOLOGICAL CHANGE IN CHANNEL ISLAND DEER MICE

Deer mice, Peromyscus maniculatus, collected over 90 years from three California Channel Islands, were examined for evidence of morphological change. Rapid morphological change has occurred in the endemic subspecies from Santa Barbara (P. m. elusus), Anacapa (P. m. anacapae), and Santa Cruz Island (P. m. santacruzae). Data were divided into two temporal classes, 1897–1941 and 1955–1988. Of the 16 morphological characters measured, between five and 10 measures changed significantly (P ⩽ 0.05) with temporal class in each subspecies, and multivariate test statistics were significant (P ⩽ 0.05) for all three subspecies. For each subspecies, depth of braincase, total length, tail length, and hind foot length became smaller over time, except depth of braincase, which became larger in P. m. elusus. The rates of change dramatically exceed those estimated from paleontological records and are even higher than those reported in some experimental selection studies. Temporal change in two characters exceeds differentiation between subspecies. Although changing, each subspecies remained well differentiated, and incorporation of temporal change allowed correct classification of most specimens. Unlike nearly all previous reports of rapid evolution, the changes in these populations were not associated with a founder events or recent introductions. This study demonstrates that rapid phenotypic change can occur in long‐established natural populations and temporal stability of morphological characters in such populations, even over short evolutionary time periods, cannot be assumed.

Rapid morphological and genetic change in Chicago-area Peromyscus

We report rapid change of morphology and mitochondrial genes in white‐footed mice (Peromyscus leucopus) in the Chicago (Illinois, USA) region. We sequenced mitochondrial DNA COX2 from 55 museum skins of white‐footed mice caught in the Chicago area since 1855 and from 44 mice recently trapped in the same locations. We found consistent directional genotype replacement at five separate collection locations. We later focused on a single one of these locations (Volo Bog State Natural Area) and sequenced mitochondrial D‐loop control region from 58 museum skins of mice collected in 1903–1976 and 32 mice recently trapped there. We found complete and more recent replacement of D‐loop haplotypes, apparently occurring between 1976 and 2001. We tested whether these genetic changes were mirrored by changes in morphology by comparing 15 external and cranial traits. We found no significant morphological differences between mice collected in 1903–1976; however, mice collected in 2001–2003 showed 9 of 15 measurements to be significantly changed relative to the earlier samples. Recent mice were longer in total length, with broader, longer noses, and longer but shallower skulls 1 . Discriminant function analysis allowed for 100% correct classification using these traits. Principal components analysis shows variance over time is well distributed across both external and cranial measures. The sequential replacements of haplotypes and the rapid change of morphology can best be explained by replacement of the regional population with immigrants from genetically distinct neighbouring populations, likely facilitated by the large environmental changes occurring over the time period. Replacement with genotypes from external populations may be a common mechanism of evolution of newly adaptive local forms in an increasingly human‐impacted world.

Mammalian microevolution: Rapid change in mouse mitochondrial DNA

We have compared the sequences of mitochondrial DNA extracted from museum skins of white-footed mice caught in the Chicago area since 1855 and from modern mice trapped alive in the same locations. We found a consistently similar directional change of mouse genotype over this period at each of five collection sites that were separated by 10–70 km. The genotype most common 100 years ago is now extremely rare, indicating that the mammalian mitochondrial genome can undergo rapid evolution.

Museum collections of mammals corroborate the exceptional decline of prairie habitat in the Chicago region

Abstract The prairie deer mouse (Peromyscus maniculatus bairdii) was more common than the white-footed mouse (P. leucopus) in museum collections from the 6 Illinois counties of the Chicago region before 1920 but constitutes only 5% of specimens deposited since 1970. Because white-footed mouse prefers woody vegetation and because prairie deer mouse is limited to prairie or large open habitats, the change in proportion is likely driven by a disproportionate loss of prairie among remaining natural habitat and increases in woody vegetation within grasslands. The decline of the prairie vole (Microtus ochrogaster) relative to the meadow vole (M. pennsylvanicus) and the lack of recent specimens of Franklins ground squirrel (Spermophilus franklinii) corroborate the hypothesis that prairie habitats have declined much more so than wooded habitats in the Chicago region. Based on extinction models using museum records, it is probable that S. franklinii is already locally extirpated. Regression analysis suggests the white-footed mouse will be the only local Peromyscus in 0–140 years.

Rapid change in mouse mitochondrial DNA

We have compared the sequences of mitochondrial DNA extracted from museum skins of white-footed mice caught in the Chicago area since 1855 and from modern mice trapped alive in the same locations. We found a consistently similar directional change of mouse genotype over this period at each of five collection sites that were separated by 10–70 km. The genotype most common 100 years ago is now extremely rare, indicating that the mammalian mitochondrial genome can undergo rapid evolution.

Rapid morphological change in black rats (Rattus rattus) after an island introduction.

Rapid morphological change has been shown in rodent populations on islands, including endemic deer mice (Peromyscus maniculatus subspp.) on the California Channel Islands. Surprisingly, most of these changes were towards a smaller size. Black rats were introduced to Anacapa Island in the mid-1800s (probably in 1853) and eradicated in 2001–2002. To assess possible changes in these rats since their introduction, eleven cranial and four standard external measurements were taken from 59 Rattus rattus specimens collected from 1940–2000. All rat cranial traits changed 3.06–10.43% (724–2567 d, 0.06–0.42 h), and all became larger. When considered in haldanes, these changes are among the fastest on record in any organism, and far exceed changes found in other island rodents. These changes were confirmed by MANOVA (Wilk’s λ < 0.0005, Fd.f.15 = 2974.386, P < 0.0005), and all 11 cranial traits significantly fit linear regressions. We speculate that concurrent changes in mice may have been due in part to competition with and/or predation by rats. Future research might evaluate whether the vector of mouse evolution on Anacapa is again changing after rat eradication.

Evaluating the Predicted Local Extinction of a Once-Common Mouse

In an earlier paper (Pergams & Nyberg 2001) we found that the proportion of the prairie deer mouse (Peromyscus maniculatus bairdii), among all local Peromyscus museum specimens collected in the Chicago region, had significantly declined over time. This proportion changed from about 50% before 1900 to <10% in the last 25 years. Based on this proportion a regression model predicted the local extinction of the prairie deer mouse in 2009. To evaluate that prediction, we estimated current deer mouse abundance by live trapping small mammals at 15 preserves in Cook and Lake counties, Illinois (USA) at which prairie deer mice had previously been caught or that still contained their preferred open habitat. In 1900 trap nights, 477 mammals were caught, including 251 white-footed mice (P. leucopus), but only one prairie deer mouse. The observed proportion of Peromyscus that were prairie deer mice, 0.4%, was even lower than the 4.5% predicted for 2000. Here we also introduce a simple, new community proportions model, which for any given geographic region compares the proportions of species recently caught with the proportions of species in museums. We compared proportions of seven species collected in Cook and Lake counties and examined by Hoffmeister (1989) with proportions of these species that we caught. Ten percent of the museum community was prairie deer mice, but only 0.2% of our catch was. The current local scarcity of the prairie deer mouse is consistent with the regression-based prediction of its eminent local extinction. More conservation attention should be paid to changes in relative abundance of once-common species.