The Tecate cypress (Cupressus forbesii) is a tree species associated with chaparral ecosystems in southern California and northern Baja California, Mexico. It is fire-adapted, its regeneration triggered by the opening of serotinous cones when adult trees are burned. Surveys made in the 1980s by others suggested that some Tecate cypress populations were declining, and some authors suggested that increased fire frequency in southern California was a major factor for this decline. We asked whether current population trends were still negative for Tecate cypress 20 years later, and whether population growth was associated with fire return interval length. Based on demographic, survival, and growth-rate data, we calculated the rate of population increase (λ) for the 4 known California populations of Tecate cypress (Coal Canyon-Sierra Peak in Orange County and Guatay Mountain, Otay Mountain, and Tecate Peak in San Diego County). The rate of population increase was positively associated with fire return interval length, which varied among populations. A 40-year or longer fire return interval corresponded to λ > 1, suggesting the population trend is positive, while a fire return interval shorter than 40 years corresponded to λ < 1, suggesting that populations burning more often than once every 40 years are declining.

Volcanic eruptions offer unique opportunities for the study of successional processes. The Paricutín Volcano eruption that started in 1943 and lasted for 9 years created different conditions for primary and secondary succession. Bare areas at the time of the eruption (mainly agricultural fields) offer an opportunity to study the effect of major natural disturbances in sites previously affected by human activities. One representative area, the Mesa de Cutzato, was surveyed to determine vegetation species composition and structure 50 years after the volcanic eruption ceased. Our results showed that few species have established and that total plant cover remained low (< 10%) and is patchy. Four species dominated these patches: Eupatorium glabratum (23% relative cover), Senecio stoechadiformis (14%), Senecio salignus (12%) and Muhlenbergia minutissima (6%). These species are either early successional or disturbance-tolerant species. No late successional species, particularly tree species, were found. Our results suggested that in old agricultural fields covered by tephra, known as arenales, succession is proceeding slowly.

A crucial need for population maintenance of epiphytic species is the location of suitable microsites on a host tree. Quantitative evaluation of epiphyte seed dispersal and germination is needed to more fully understand successful host colonization; this process is especially important in dry forests, where drought and oligotrophy diminish population growth rates. In a 3-year field experiment, we evaluated seed dispersal and germination of Tillandsia brachycaulos and explored some environmental factors affecting these life-cycle phases. There was significant variation in dispersal curves depending on year and height of seed release. Forty-one percent of seeds experimentally released were not dispersed and only ca. 0.5% of dispersed seeds were captured in seed traps. The number of trapped seeds decreased with distance; most seeds were captured within 1.5 m of the seed source. Seeds dispersed farther (15 m) when released from greater heights. Seed germination under controlled conditions (98%) was higher than in a field experiment (3%). Neither year nor tree height significantly affected germination of T. brachycaulos. Differences in seed dispersal and germination among years could result from variable precipitation. Establishment of new genets seems to be an important bottleneck for population growth in T. brachycaulos. Our results show that seed dispersal and germination are processes that determine such establishment.

Purple loosestrife (Lythrum salicaria) constitutes an invasive species detrimental to wetland habitats in North America. To estimate areas vulnerable to it in Kansas, we modeled the potential geographic distribution of the species by using current records in the state, remotely sensed vegetation-index data from the Moderate Resolution Imaging Spectrometer (MODIS), and the Genetic Algorithm for Rule-Set Prediction (GARP). Models built using only localities from northeastern Kansas (the origin of invasion within the state) consistently predicted test localities in other parts of the state with negligible omission. An additional analysis using records from all counties where the species is known showed a similar prediction. All models indicated suitable conditions for purple loosestrife in much of eastern and central Kansas, as well as in riverine and irrigated areas in the western part of the state. The approach presented here might prove useful for assessing the regional colonization potential of other newly detected invasive species before other studies can be undertaken.

Nickel hyperaccumulator plants contain at least 1,000 µg Ni/g dry mass. Their high-Ni tissues present a chemically unique resource for herbivorous insects. A prior survey of insects associated with the Ni hyperaccumulator Streptanthus polygaloides in California yielded a new species, Melanotrichus boydi Schwartz and Wall (Hemiptera: Miridae). Here we document the host preference of M. boydi. Surveys of 10 S. polygaloides populations across its geographical and elevational ranges documented the presence of M. boydi upon S. polygaloides at all sites. A host-choice experiment contrasting M. boydi with the polyphagous mirid Lygus hesperus (both collected from S. polygaloides) showed M. boydi preferred S. polygaloides but L. hesperus did not. Other host-choice studies showed M. boydi preferred S. polygaloides to 2 other ultramafic soil plant species in the Brassicaceae, including another species of Streptanthus. No preference was observed when M. boydi was offered samples from several populations of S. polygaloides or given a choice between high-Ni and low-Ni S. polygaloides plants. These results show that M. boydi feeds primarily on S. polygaloides but lacks population-level specificity. This is the first report of a North American insect species monophagous on a Ni hyperaccumulator species.

Humans have introduced organisms into many new and often novel environments. These changes in organism distributions provide us an opportunity to directly observe the ecological and evolutionary processes that influence adaptation. Here we examine the suitability of a variety of introduced legume species, plus several non-host native species, for the development of Stator limbatus larvae. About half of the species examined were capable of supporting larval development, though larval survival was high on few non-host species. Maternal experiences during egg maturation affected larval survival on seeds of Parkinsonia aculeata and Ebenopsis ebano, but not on any other non-hosts; females that matured eggs in contact with seeds of Parkinsonia florida, a native host of S. limbatus in the Sonoran Desert, produced larger eggs and had offspring with higher survival on seeds of these 2 exotic species than if females did not encounter P. florida during egg maturation. Using a half-sib breeding design, we detected genetic variation in larval survival on seeds of P. aculeata, but found that maternal experience during egg maturation (whether or not females encountered seeds of P. florida) was the major factor affecting offspring survival on P. aculeata. We conclude that the ability of S. limbatus larvae to survive on some non-native plant species depends on the species composition of the local plant community – female experiences with P. florida induce changes in egg size and composition that subsequently influence survival of larvae on seeds of the novel host, P. aculeata.

The distribution and abundance of the endangered Baja California killifish, Fundulus lima, and its interaction with exotic fishes were studied in oases of the central part of Baja California peninsula, Mexico (Río San Ignacio and Río La Purísima basins), from October 2002 to July 2004. Five fish species were recorded: the native killifish and 4 exotics (Cyprinus carpio, Poecilia reticulata, Xiphophorus hellerii, and Tilapia cf. zillii). Two new populations of the killifish are reported for the Río San Ignacio as well as confirmation of occurrence in the upper Río La Purísima. Density of the killifish in the Río San Ignacio showed a significant inverse correlation with that of the exotic redbelly tilapia (Tilapia cf. zillii). Baja California killifish densities in both rivers decreased significantly after the hurricane-induced flood event of 23 September 2003, but exhibited notable recovery 10 months later. Relative abundance of killifish at the type locality, San Ignacio oasis, decreased significantly during an 8-year period after introduction of tilapia. The status of Baja California killifish should be changed from threatened to endangered to reflect continued reductions in distribution as result of proliferation of nonnative fishes, particularly redbelly tilapia. Management efforts to reduce abundance of exotic fishes are needed to ensure persistence of the endemic Baja California killifish.

Two atherinid species, Labidesthes sicculus (brook silverside) and Menidia beryllina (inland silverside), often co-occur in North American reservoirs. Menidia beryllina is a superior competitor for zooplankton and has displaced Labidesthes in a number of reservoir habitats. In Lake Texoma (Oklahoma-Texas), Labidesthes was thought extirpated from the reservoir after introduction of Menidia in the 1950s, but several recent populations were discovered in down-lake coves with established marinas. Artificial lighting from marinas might benefit Labidesthes by attracting terrestrial insects in these habitats. We conducted a field experiment to test effects of artificial lighting and abundance of Menidia on growth and diet of Labidesthes. Dry weight of Labidesthes at the end of our experiment was significantly higher in artificially lit treatments than in dark treatments, but there was no significant effect of Menidia abundance on weight of Labidesthes. We concluded this effect was attributed to greater availability of dipterans, which dominated the diet of Labidesthes, under artificial lights. Whereas Menidia is a more efficient planktivore than Labidesthes, increased abundance of dipterans near marinas likely promotes the coexistence of these 2 species.

Understanding how and why the abundance of a species changes in space and time is an essential component to effective endangered species conservation. Key to this understanding is being able to distinguish natural population dynamics from a downward trajectory of a species at risk of extinction. For many species in arid environments, rainfall drives population changes. This is the case for Coachella Valley fringe-toed lizards (Uma inornata), a species listed as threatened under the U.S. Endangered Species Act. At low rainfall levels, the lizards exhibit negative population growth until annual precipitation exceeds 40 to 50 mm. Fluctuation in the population growth of the lizards is also correlated with changes in their diet. A regression model using rainfall and diet to explain lizard population dynamics resulted in a significant R² value of 0.956. Because drought is common in their arid environment, it is not unusual for this lizard species to endure consecutive years of population declines. Fringe-toed lizard population counts during extended droughts often approach zero, yet the populations quickly rebound during periods of near average rainfall. If counts approaching zero are not reliable thresholds for when remedial management actions are warranted, then monitoring based management decisions need to use criteria that are more heuristic. Departures from the rainfall-diet-population growth model might provide the signal needed for management actions.

Various grassland bird species have displayed population declines over the past 30 to 40 years, and interest in explaining possible causes for the declines has prompted numerous studies. Many of these studies have focused on changes in agricultural practices; few have evaluated possible effects of the presence of nonnative grasses in grasslands. The objective of our study was to determine the effects a nonnative grass, Old World bluestem (OWB; Bothriochloa ischaemum), might have on grassland bird species abundance and richness, and on bird food availability (arthropod biomass). Three pastures each of native range, expired Conservation Reserve Program (CRP), and OWB were sampled from May to July 2001 in Comanche County, Kansas. Bird abundance and species richness were assessed by using a point-count method along 3 transects in each pasture. Food availability was estimated by collecting arthropods along 10 transects in each pasture by sweep-netting. Results showed significantly lower bird abundance and species richness in OWB pastures than in native pastures. OWB pastures also had significantly less arthropod biomass than native pastures. Because food availability (arthropod biomass) was directly related to percent forb cover within fields and was mostly absent in OWB pastures, we contend these were the primary factors contributing to lower avian richness and abundance in OWB fields when compared to CRP and native pastures.

The Chiricahua fox squirrel (Sciurus nayaritensis chiricahuae) is an uncommon subspecies endemic to the Chiricahua Mountains of southeastern Arizona. We monitored annual cycles of body mass and reproduction to elucidate factors shaping the ecology of the sexes. Body mass of adult males did not fluctuate seasonally, although males tended to be heavier in winter. Body mass of adult females fluctuated seasonally, with lower body masses in summer than winter. Males and females did not differ in body mass in summer and fall, but females were heavier than males in winter and spring. Males with scrotal testes were found in the population during all seasons, but were especially prevalent in winter and spring. The majority of lactating females were present in spring and summer. Annual cycles in reproduction and body mass of Chiricahua fox squirrels are similar to more widespread species of tree squirrels, although males did not exhibit typical body mass fluctuations. Extreme spatial and temporal fluctuations of food experienced by Chiricahua fox squirrels might result in annual patterns in space use and body mass that differ from tree squirrels living in forests with a greater abundance of food.

Velvet ants (Hymenoptera: Mutillidae) of the Bitter Lake National Wildlife Refuge were collected and studied over a 4-year period (1996 to 1999). The study resulted in the collection of at least 52 species in 6 genera. It also resulted in the discovery and description of the previously unknown male of Dasymutilla calorata Mickel, plus the discovery and description of 2 new species.

Honeybees (Apis mellifera) in the Americas are an introduced species that has been established throughout most of the hemisphere for decades or centuries. An exception is the uninhabited Midriff islands in the Gulf of California. Except for the near-shore Isla Tiburón, historical evidence indicates that feral honeybees did not successfully colonize the Midriff islands until about the early 1990s. Today, colonies are well established on the major islands of Tiburón, San Esteban, San Lorenzo, and Ángel de la Guarda, and honeybees forage on 2 smaller islands: Las Ánimas (San Lorenzo Norte) and Mejía. There is no evidence of colonization or foraging on the small and floristically impoverished islands of Salsipuedes, Rasa, Partida Norte, and San Pedro Mártir. Whether the honeybees are Africanized remains undetermined, but is likely in view of the overwater distances to the islands and time of their arrival. Whether Africanized or not, honeybees are an invasive exotic species that could significantly disrupt the largely natural Midriff island ecosystems.

Cercyonis pegala, a butterfly whose geographic and temporal distribution in Mexico is poorly known, is reported from Coahuila State for the first time, from the Valle de Cuatro Cienegas. This area is composed of a unique vegetational community in which C. pegala was not formerly known to occur.

We report an apparently successful effort to restore native fishes to a pool in the Cuatro Ciénegas Bolsón, Coahuila, Mexico. The results demonstrate the feasibility, in small, confined systems, of eliminating a recently introduced nonnative fish, the spotted jewelfish (Hemichromis guttatus), and transplanting a native fish assemblage from nearby areas. We recommend that similar removal and restoration activities be conducted to protect the unique, highly endemic Cuatro Ciénegas fish fauna.

The diploid checkered whiptail lizard, Aspidoscelis tesselata, is a parthenogenetic species that occupies semiarid habitats in the southwestern USA. It comprises several morphologically distinct pattern classes that occasionally coexist within the same geographical area. Two pattern classes, C and E, coexist on both sides of Sumner Lake and the Pecos River in Sumner Lake State Park, De Baca County, New Mexico. Individuals of pattern class C are larger than individuals of pattern class E (they also produce larger clutches and take longer to reach reproductive maturity). Herein we present analyses of the stomach contents of specimens collected at Sumner Lake to determine if these 2 pattern classes show differences in their diets. Termites made up over 70% of the prey items found in the stomachs of both pattern classes, but when analyzed by volume, the most important prey were cicadas, planthoppers, and short-horned grasshoppers for pattern class C, and short-horned grasshoppers, cicadas, long-horned grasshoppers, termites, and scarab beetles for pattern class E. Considering prey other than termites, pattern class C lizards tended to consume larger prey items than did pattern class E lizards. Aside from this size-related difference, the diet of the 2 pattern classes at Sumner Lake was similar. This lends support to the hypothesis that body size and reproductive differences between the 2 pattern classes are genetically based.

Many interspecific commensal foraging interactions involving birds have been documented. We describe an observation of commensal foraging by a fan-tailed warbler (Euthlypis lachrymosa) with a nine-banded armadillo (Dasypus novemcinctus) in Guerrero, southwestern Mexico. Our observation is similar to those reported from El Salvador by (Komar and Hanks, 2002) and indicates this association between fan-tailed warblers and nine-banded armadillos is more widespread than previously reported.

We present the first documented account of adult greater roadrunner (Geococcyx californianus) feeding on California least tern chicks (Sterna antillarum browni). This predation event occurred at a designated nesting site within Batiquitos Lagoon, San Diego County, California, in 1996. We hypothesize that the concentrated foraging efforts by the roadrunner were an opportunistic response to a localized abundance of favorable prey items, which warrants an increased awareness at other least tern nesting sites situated in close proximity to greater roadrunner habitat.

We report the karyotypes of Reithrodontomys hirsutus and R. mexicanus from Oaxaca and Puebla, Mexico, and R. sumichrasti from Puebla and Veracruz, Mexico; the first is described for the first time and the latter 2 represent karyotypic variants from localities different from those previously reported. Our findings confirm the complex chromosomal evolution that has occurred within the genus Reithrodontomys and support molecular data indicating that an undescribed species inhabits the highlands of the Sierra Madre Oriental in Mexico. We also document chromosomal variation within R. sumichrasti congruent with phylogenetic patterns reported previously.

Before 1500, the western Great Plains was occupied by 3 sympatric wild canid species, which is the general rule throughout most of the world. However, during the past 100 years, substantial changes to the canid community have occurred in this region. During research on canids in the panhandle of Texas from 1998 to 2001, we documented 5 canid species within 5 km of each other, although there was apparent habitat segregation among species. This is the highest reported number of canid species at a given location in North America and indicates that recent human activities have increased the biodiversity of canids throughout the western Great Plains.

We conducted spotlight counts along a 41-km transect to estimate population density and habitat use of mule deer (Odocoileus hemionus), an introduced mammalian herbivore on Santa Catalina Island, California. Mean population density, calculated using distance-sampling procedures, was 5.41 deer/km² (95% CI: 4.40, 6.65) during the 11 months of our study. Deer used island chaparral, human-developed areas, and to a lesser degree, riparian vegetation more than expected, and bare areas, grasslands, and woodlands less than expected, based on the availability of these habitats in our study area.

Although feral hogs (Sus scrofa) have expanded their range into the Chihuahuan Desert of Texas, little information is available on their ecology. We determined that the summer diet of feral hogs (n  =  28) in the Davis Mountains of Texas was dominated by herbaceous material (38.6%) and roots and tubers (34.3%). Further investigation is needed to determine the impact of feral hog foraging behavior on the fragile floral and faunal communities of the Chihuahuan Desert.

Mountain lions (Puma concolor), throughout their distribution, eat a variety of prey, but primarily consume large prey (e.g., cervids). While monitoring radio-collared mountain lions, we saw a mountain lion kitten consuming a Texas tortoise (Gopherus berlandieri). Small prey might increase survival of young mountain lions developing predation skills required for solitary survival as adults.