Distribution and habitat of endangered American burying beetle in northern and southern regions

The American burying beetle, Nicrophorus americanus, is a federally endangered insect that once occurred in 35 US states and 3 Canadian provinces. Today, it remains at the periphery of its former range with the largest populations concentrated in Nebraska and Oklahoma. We assessed beetle occurrence records throughout the western ranges in Nebraska and Oklahoma, but excluded a small eastern population on Block Island, Rhode Island. We compiled more than 2500 presence–absence records and used GIS-based random forest models to create distribution maps throughout the current western range of the American burying beetle based on habitat characteristics within 800 m of each trap. We also used generalized linear models to identify habitat characteristics associated with N. americanus occurrences and to document differences between northern and southern habitat associations. In its northern range, N. americanus was associated with wetter areas while avoiding agricultural and urban areas. In the southern range, N. americanus was associated with sandy soils, hayfields, and native forests and grasslands, while avoiding human population centers and agricultural areas. Our N. americanus distribution maps for the northern and southern regions highlight areas where N. americanus is likely to occur, providing a tool that may improve current management. This first attempt at a range-wide model of American burying beetle occurrences revealed important differences among regions and can improve region-specific management and conservation.     

Population genetics and symbiont assemblages support opposing invasion scenarios for the red turpentine beetle (Dendroctonus valens)

Exotic forest insects and their symbionts pose an increasing threat to forest health. This is apparently true for the red turpentine beetle (Dendroctonus valens), which was unintentionally introduced to China, where the beetle has killed millions of healthy native pine trees. Previous population genetics studies that used cytochrome oxidase I as a marker concluded that the source of D. valens in China was western North America. In contrast, surveys of fungi associated with D. valens demonstrated that more fungal species are shared between China and eastern North America than between China and western North America, suggesting that the source population of D. valens could be eastern North America. In this study, we used microsatellite markers to determine population structure of D. valens in North America as well as the source population of the beetle in China. The analyses revealed that four genetically distinct populations (herein named the West, Central, Northeast and Mexico) represent the native range of D. valens. Clustering analyses and a simulation‐based approximate Bayesian computation (ABC) approach supported the hypothesis that western North America is the source of the invasive D. valens population. This study provides a demonstration of non‐congruence between patterns inferred by studies on population genetics and symbiont assemblages in an invasive bark beetle.     

A Review of Hypotheses of Decline of the Endangered American Burying Beetle (Silphidae: Nicrophorus americanus Olivier)

The largest species of North American Nicrophorus (Coleoptera: Silphidae), N. americanus, was placed on the US federal list of endangered species in 1989. This paper reviews literature bearing on eight hypotheses that attempt to explain the dramatic decline of this species over 90% of its former range. What is known regarding each hypothesis is separated from what remains to be investigated. We find that although progress has been made during the past 12 years, even the most well supported hypothesis requires a number of important studies to be completed or extended before we can confidently explain the decline of this species and predict the success of conservation efforts.     

Deep phylogeographical structure and parallel host range evolution in the leaf beetle Agelasa nigriceps

To understand the mechanisms behind the diversification of herbivorous insects through insect–plant interactions, it is important to know how the insects change their diet breadth in response to environmental changes. In this study, we investigated the phylogeographical pattern of the leaf beetle Agelasa nigriceps to infer the evolutionary history of its host range. While this beetle commonly uses Actinidia arguta (Actinidiaceae) as a host plant, it has been recorded recently on Pterostyrax hispidus (Styracaceae), which is now increasing in abundance at some localities in Japan due to the indirect effects of high population size of a mammalian herbivore. Considerable variation among populations in the ability of Ag. nigriceps to use P. hispidus suggests that P. hispidus is a newly acquired host plant for this beetle. Phylogenetic analyses using mitochondrial DNA sequences and amplified fragment length polymorphism (AFLP) revealed a high degree of phylogeographical structure in Ag. nigriceps throughout Japan, which is consistent with the hypothesis that several glacial refugia existed in the Japanese archipelago. In contrast, no genetic structure associated with the host plants was detected. Both the mitochondrial DNA and AFLP analyses showed that populations that can use P. hispidus are polyphyletic. These results and geographical variation in host use suggest that the host range expansion to a novel host, P. hispidus, is a very recent and possibly ongoing phenomenon and has occurred independently in several regions. Our study illustrates that the host range of herbivorous insects can evolve repeatedly in response to similar environmental changes.     

Horizontal transmission of a microsporidium from the convergent lady beetle, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), to three coccinellid species of Nova Scotia

Convergent lady beetles, Hippodamia convergens Guérin-Méneville, are a popular choice for aphid control in North America. An unidentified microsporidium was found in H. convergens adults that were purchased from a commercial insectary in 2004. This study examined egg cannibalism and egg predation as a means of horizontal transmission of the unidentified microsporidium among H. convergens larvae and three coccinellid species found in Nova Scotia: Coccinella septempunctata (seven-spotted lady beetle), C. trifasciata perplexa (three-banded lady beetle), and Harmonia axyridis (multicolored Asian lady beetle). The microsporidium was transmitted with 100% efficiency when first instars fed on microsporidia-infected eggs. Mean spore count data from smear preparations of infected beetles suggest that the infection was as heavy in C. trifasciata perplexa (a native coccinellid) (11.2 ± 0.96 spores/100 μm²) as it was in H. convergens (the natural host) (12.8 ± 1.16) but lighter in the introduced species C. septempunctata (7.5 ± 0.65) and H. axyridis (0.8 ± 0.11). For all of the beetle species examined, larval development was significantly longer for microsporidia-infected individuals than for their uninfected cohorts. The microsporidium had no effect on larval mortality. Based on the results of this study, field-collected H. convergens should be examined for microsporidia and uninfected individuals should be used to rear individuals for release in biological control programs. However, this is unlikely to happen because H. convergens are relatively easy and inexpensive to collect from their overwintering sites for redistribution.     

Parasites,info-disruption,and the ecology of fear

There is growing interest in the ecological consequences of fear, as evidenced by the numerous studies on the nonconsumptive, trait-mediated effects of predators. Parasitism, however, has yet to be fully integrated into research on the ecology of fear, despite it having direct negative and often lethal effects on hosts and being the most common life history strategy on the planet. This might at least be partly due to the traditional, but untested, assumption that anti-parasite responses are weak relative to anti-predator responses. To test this hypothesis, we quantified the activity and location responses of Bufo americanus tadpoles to one of six chemical cues: water; cercariae of Echinostoma trivolvis, a trematode which infects and can kill amphibians; a snail releasing E. trivolvis cercariae; an uninfected snail; food; or conspecific alarm chemicals signaling predation. There is also literature encouraging research on the context dependency and pollution-induced disruption of fear responses. Consequently, before quantifying responses to the chemical cues, half of the B. americanus were exposed to the herbicide atrazine (201 μg/l for 4 days), a reported inhibitor of fear responses in fish. Tadpoles were attracted to food, were indifferent to an uninfected snail, avoided alarm chemicals, and exhibited avoidance and elevated activity in response to a snail shedding cercariae and cercariae alone. Atrazine had no detectable effects on B. americanus’ responses to the tested cues despite the use of a higher concentration and longer exposure duration than has been repeatedly shown to inhibit chemical cue detection in fish. The magnitude of anti-parasite and anti-predator responses were qualitatively similar, suggesting that the fear of disease and its ecological consequences could be comparable to that of predation. Consequently, we call for a greater integration of parasites into research on the ecology of fear and trait-mediated indirect effects.     

Altitudinal change in soil and foliar nutrient concentrations and in microclimate across the tree line on the subtropical island mountain Mt. Teide (Canary Islands)

Mt. Teide (Tenerife, Spain) is a high volcanic island mountain with an unusually low tree line elevation (2000–2100 m). While searching for the causes of this tree line depression, we analysed the concentrations of total N, available P, and salt-exchangeable Ca, K and Mg in three soil horizons, and the foliar N, P, Ca, K and Mg concentrations in six abundant plant species (trees, shrubs, forbs) along a transect from 1400 (1600) to 3100 m a.s.l. The objective of the study was to detect altitudinal trends in soil and plant nutrient status below and above the tree line. For characterising elevational changes in microclimate and hydrology, we also conducted measurements of air and soil temperatures (T_a and T_s), atmospheric water vapour saturation deficit (D), potential evaporation (E) and soil moisture (θ) on 3–4 occasions along the transect.T_a and T_s did not linearly decrease with elevation but were highest at or immediately below the tree line and were relatively low in the closed Pinus canariensis forest at 1600 m. T_s reached maxima at about 70 °C near the tree line. The absence of a linear temperature decrease with elevation was caused by a stable temperature inversion at about 2000 m and by canopy shading in the forest canopy below the tree line. In June, the topsoil (10 cm) dried out almost completely between 1800 and 3100 m, but remained moist in the pine forest at 1600 m. This gradient reflects the transition from the montane cloud belt to the dry alpine belt higher upslope. The subsoil (30 cm) contained >30 vol% of soil water at all elevations even in June except for the uppermost site (3100 m). Potential evaporation increased with elevation despite a decrease in D. We assume that this is mainly due to the air pressure-dependent increase with elevation in the diffusion coefficient for water vapour in air.The concentrations of N and ‘available’ P (after Olsen) in the mineral topsoil were by far smaller than in alpine soils of other humid mountains which is thought to be a consequence of a very dry and biologically inactive topsoil in the semi-arid alpine belt of Mt. Teide. In contrast to many other mountains, foliar N, P and cation concentrations in the plants did not increase with elevation but either remained unchanged, or decreased as in the tree line species P. canariensis. Nevertheless, P. canariensis probably is not limited by nutrient deficiency at the tree line despite rather low N and P needle concentrations. Rather, drought and heat stress effects on seedling establishment are thought to be the causes of the tree line depression.     

Changes in ground beetle assemblages above and below the treeline of the Dolomites after almost 30 years (1980/2009)

Very little is known about the changes of ground beetle assemblages in the last few decades in the Alps, and different responses to climate change of animal populations living above and below the treeline have not been estimated yet. This study focuses on an altitudinal habitat sequence from subalpine spruce forest to alpine grassland in a low disturbance area of the southeastern Dolomites in Italy, the Paneveggio Regional Park. We compared the ground beetle (Carabidae) populations sampled in 1980 in six stands below and above the treeline (1650–2250 m a.s.l.) with those sampled in the same sites almost 30 years later (2008/9). Quantitative data (species richness and abundance) have been compared by means of several diversity indexes and with a new index, the Index of Rank‐abundance Change (IRC). Our work shows that species richness and abundance have changed after almost 30 years as a consequence of local extinctions, uphill increment of abundance and uphill shift of distribution range. The overall species number dropped from 36 to 27, while in the sites above the treeline, species richness and abundance changed more than in the forest sites. Two microtherm characteristic species of the pioneer cushion grass mats, Nebria germari and Trechus dolomitanus, became extinct or showed strong abundance reduction. In Nardetum pastures, several hygrophilic species disappeared, and xerophilic zoophytophagous elements raised their population density. In forest ecosystems, the precipitation reduction caused deep soil texture and watering changes, driving a transformation from Sphagnum‐rich (peaty) to humus‐rich soil, and as a consequence, soil invertebrate biomass strongly increased and thermophilic carabids enriched the species structure. In three decades, Carabid assemblages changed consistently with the hypothesis that climate change is one of the main factors triggering natural environment modifications. Furthermore, the level of human disturbance could enhance the sensitivity of mountain ecosystems to climate change.     

El Niño impacts on human-modified tropical forests: Consequences for dung beetle diversity and associated ecological processes

Our knowledge of how tropical forest biodiversity and functioning respond to anthropogenic and climate-associated stressors is limited. Research exploring El Niño impacts are scarce or based on single post-disturbance assessments, and few studies assess forests previously affected by anthropogenic disturbance. Focusing on dung beetles and associated ecological functions, we assessed (a) the ecological effects of a strong El Niño, (b) if post-El Niño beetle responses were influenced by previous forest disturbance, and (c) how these responses compare between forests impacted only by drought and those affected by both drought and fires. We sampled 30 Amazonian forest plots distributed across a gradient of human disturbance in 2010, 2016, and 2017—approximately 5 years before, and 3–6 and 15–18 months after the 2015–16 El Niño. We found 14,451 beetles from 98 species and quantified the beetle-mediated dispersal of >8,600 seed mimics and the removal of c. 30 kg of dung. All dung beetle responses (species richness, abundance, biomass, compositional similarity to pre-El Niño condition, and rates of dung removal and seed dispersal) declined after the 2015–16 El Niño, but the greatest immediate losses (i.e., in 2016) were observed within fire-affected forests. Previous forest disturbance also influenced post-El Niño dung beetle species richness, abundance, and species composition. We demonstrate that dung beetles and their ecological functions are negatively affected by climate-associated disturbances in human-modified Amazonian forests and suggest that the interaction between local anthropogenic and climate-related stressors merits further investigation.     

Tidal marsh plant responses to elevated CO2, nitrogen fertilization,and sea level rise

Elevated CO₂ and nitrogen (N) addition directly affect plant productivity and the mechanisms that allow tidal marshes to maintain a constant elevation relative to sea level, but it remains unknown how these global change drivers modify marsh plant response to sea level rise. Here we manipulated factorial combinations of CO₂ concentration (two levels), N availability (two levels) and relative sea level (six levels) using in situ mesocosms containing a tidal marsh community composed of a sedge, Schoenoplectus americanus, and a grass, Spartina patens. Our objective is to determine, if elevated CO₂ and N alter the growth and persistence of these plants in coastal ecosystems facing rising sea levels. After two growing seasons, we found that N addition enhanced plant growth particularly at sea levels where plants were most stressed by flooding (114% stimulation in the + 10 cm treatment), and N effects were generally larger in combination with elevated CO₂ (288% stimulation). N fertilization shifted the optimal productivity of S. patens to a higher sea level, but did not confer S. patens an enhanced ability to tolerate sea level rise. S. americanus responded strongly to N only in the higher sea level treatments that excluded S. patens. Interestingly, addition of N, which has been suggested to accelerate marsh loss, may afford some marsh plants, such as the widespread sedge, S. americanus, the enhanced ability to tolerate inundation. However, if chronic N pollution reduces the availability of propagules of S. americanus or other flood‐tolerant species on the landscape scale, this shift in species dominance could render tidal marshes more susceptible to marsh collapse.     

Adults of the cerambycid beetle Megacyllene caryae use both olfactory and visual information to locate mates

Many species of beetles in the family Cerambycidae use volatile pheromones to facilitate the location of mates. Visual cues may also influence the location of mates, as the adults of many species of cerambycids are often brightly patterned and diurnal. Theory predicts that combining signals or cues of different modalities (e.g., chemical, visual) to transmit information will increase the likelihood of an organism responding to this information, compared to when the signal or cue is presented alone. Here, we test the hypothesis that attraction of adults of the cerambycid beetle Megacyllene caryae (Gahan) (Coleoptera: Cerambycidae, Clytini) to their pheromones will be increased when visual cues are present. Consistent with that hypothesis, the number of beetles caught by traps baited with pheromones was increased 3.4‐fold when a dead adult beetle of that species was attached to the trap, relative to those with just pheromone alone. Capture of M. caryae in our study was also influenced by the position of traps within forest stands, with traps at 100 m within stands catching 2.5× as many beetles as traps at the forest edge. These findings suggest that vision and visual cues play an important role in the location of mates by cerambycid beetles and warrant further research. Also, the inclusion of visual cues on traps may enhance the efficacy of trapping cerambycid beetles, such as the detection of species that are non‐native and potentially invasive, or when monitoring species that are native and of conservation concern.     

Evaluation of the field impact of an adventitious herbivore on an invasive plant,yellow toadflax,in Colorado,USA

Although some introduced plants arrive into their new range without their generalist and specialist herbivores, for others, their herbivores arrive prior to, with, or after the introduction of the plant, reestablishing the link between natural enemies and invaders in the introduced range. Research documenting the effects of adventitiously introduced herbivores on their target plants in the introduced range, and the mechanisms by which those effects occur, can provide insight into potential biological weed control. We studied the effects of an accidentally introduced beetle Brachypterolus pulicarius on the growth and reproduction of its host, the invasive plant Linaria vulgaris (yellow toadflax), growing under field conditions across multiple years and sites in western Colorado, USA. We found that feeding by B. pulicarius on L. vulgaris was variable among 3 years (2002–2004) and across eight local sites. Part of the variation in damage was explained by ramet density; sites with greater ramet density experienced a higher proportion of damage. In an observational study across 2 years, damage was positively correlated with estimates of sexual reproduction, ramet growth, and clonal shoot production. However, opposite trends were observed in an experiment; damage by B. pulicarius decreased estimates of sexual reproduction. Differences between the results of the observational and experimental studies were likely driven by selective feeding by B. pulicarius on larger ramets. Nonetheless, the ability of B. pulicarius to control established L. vulgaris population growth remains uncertain under the environmental conditions we studied. In both the observational and experimental study, B. pulicarius did not affect L. vulgaris survival, and we found no evidence that established L. vulgaris populations were seed limited, suggesting that reductions in seeds may not translate into demographic changes in heavily infested populations. Interactions among insect foraging behavior, individual plant responses to damage, and the demographic consequences of seed input may help to explain the varying degrees to which herbivores affect plants and populations in this and other systems.     

Demographic characteristics of the copepod <Emphasis Type="Italic">Acanthocyclops americanus</Emphasis> (Sars, 1863) (Copepoda: Cyclopoida) fed mixed algal (<Emphasis Type="Italic">Scenedesmus acutus</Emphasis>)-rotifer (<Emphasis Type="Italic">Brachionus havanaensis</Emphasis>) diet

The predatory copepod Acanthocyclops americanus is commonly found in shallow ponds and lakes in Mexico. We tested the survivorship and reproduction-related variables of this copepod, isolated from Lake Huetzalin (Xochimilco, Mexico City), on four mixed diets comprising two algal concentrations (0.8 × 10⁶ and 1.6 × 10⁶ cells ml⁻¹ of Scenedesmus acutus) and two rotifer densities (1 and 8 ind. ml⁻¹ of Brachionus havanaensis). Survivorship patterns of naupliar and adult stages of A. americanus were evaluated at 24 ± 1°C. The demography experiments were initiated with five females and five males (1:1 ratio, 5th copepodites) into each of the 16 test [= 4 diet combinations × 4 replicates (cohorts)] jars containing 50 ml medium and with one of the chosen algal-rotifer diets. Data on the survival of naupliar and copepodites (up to V) showed a high death rate (80%) in A. americanus by the time nauplii reached the adult stage. The duration of developmental time for nauplii and the copepodite V (C-V) was about 28 days by which time A. americanus became adults. Food combination had a significant effect on both survival and duration of the naupliar and C-V but not on the development time in C-I, C-II, C-III, and C-IV. Naupliar stages showed highest life expectancy at low food levels (rotifers or alga). Adult male and female copepods showed better survival under higher availability of rotifers in the medium, while higher algal density resulted in steep mortality during the first days. Average adult lifespan and life expectancy of A. americanus varied from 19 to 23 days, depending on the diet combination. Age-specific reproductive output (m _x ) of female A. americanus showed low reproduction (<10 offspring per female on any given day) when raised on low rotifer density, regardless of the algal concentration. On the other hand, enhanced offspring production (average of about 50 nauplii per female) was recorded when the rotifer density was higher (i.e., 8 ind. ml⁻¹). Gross and net reproductive rates varied from 48 to 438 and 27 to 318 offspring per female, respectively. In general, higher availability of rotifers in the medium resulted in higher (8–10 times as compared to those in low rotifer density) gross and net reproductive rates. There was no significant difference in the generation time (13–14 days) in relation to the diet combination. The rate of population increase (r) (range: 0.29–0.69 per day) increased with greater abundance of B. havanaensis in the medium. Thus, our study showed that inclusion of animal protein in the diet is necessary for high population growth rates of A. americanus.     

Impacts of the emerald ash borer (EAB) eradication and tree mortality: potential for a secondary spread of invasive plant species

Since the discovery of the emerald ash borer in 2002, eradication efforts have been implemented in an attempt to eliminate or contain the spread of this invasive beetle. The eradication protocol called for the removal of every ash tree within a 0.8 km radius around an infested tree. In 2005 this study was established to identify environmental changes attributed to the eradication program and measure subsequent shifts in forest community composition and structure. We conducted this study in Ohio and compared areas that received the eradication treatment (ash trees cut down), to areas that were left uncut, (ash still standing). The goal of this project was to identify how the plant community is responding in these two areas. The eradication protocol accelerated the formation and size of gaps within the forest and thus increased the duration and intensity of light penetrating through to the forest floor. In addition, the use of track vehicles for removal of cut trees resulted in significant soil compaction. The resultant plant community had greater species diversity (H′). When specific species composition differences were compared, an increase in the establishment of invasive plant species was detected in areas that received eradication efforts compared to those that did not. Invasive species accounted for 18.7% of the total herbaceous cover in this highly disturbed environment which included Cirsium arvense, Rhamnus cathartica and 2 species of Lonicera. In contrast, invasive species accounted for <1% of the total herbaceous cover in the undisturbed uncut areas.     

Susceptibility of small honey bee colonies to invasion by the small hive beetle,Aethina tumida (Coleoptera,Nitidulidae)

Weak and small honey bee colonies are supposed to be more susceptible to infestations by the small hive beetle [Aethina tumida, small hive beetle (SHB)]. To test this, we established 24 nucleus colonies [12 with and 12 without previous SHB removal (= screening)]. Four weeks later, we compared beetle numbers and the occurrence of SHB reproduction to the corresponding full‐sized colonies. Full‐sized colonies with no screening were infested with significantly more SHBs than all other groups (mean ± standard deviation = 46.9 ± 26.7). Regardless of this, none of the full‐sized colonies showed damage or evidence of SHB reproduction. In contrast, five nucleus colonies collapsed and SHB larvae were found in an additional seven colonies. Our study demonstrates that SHB infestation levels which are harmless to full‐sized colonies may have a negative impact on small nucleus colonies.     

Late Quaternary climatic vegetational shifts in an ecological transition zone of northern Madagascar: insights from genetic analyses of two endemic rodent species

The Loky‐Manambato region, located in northern Madagascar, is a biotically rich contact zone between different forest biomes. Local current forest cover is composed of both humid and dry formations, which show elevational stratification. A recent phylogeographical study of a regional dry forest rodent, Eliurus carletoni (subfamily Nesomyinae), found genetic evidence of forest contractions between 18 750 and 7500 years BP, which based on extrapolation of the pollen subfossil record, was thought to be associated with an expansion of local humid forests. Herein, we conduct a genetic test of this hypothesis and focused on populations on two neighbouring massifs of forest‐dependent rodent species, one associated with low‐elevation dry forests (E. carletoni) and the other with higher elevation humid forests (Eliurus tanala). Using mitochondrial markers and a combination of traditional and coalescent‐based phylogeographical, historical demographic and population genetic methods, we found evidence of historical connections between populations of E. tanala. Adjacent populations of E. carletoni and E. tanala exhibit opposite historical demographic patterns, and for both, evidence suggests that historical demographic events occurred within the last 25 000 years BP. These findings strongly support the proposed late Quaternary shifts in the floristic composition of the Loky‐Manambato region.     

Relationships between the density of two potential restoration tree species and plant species abundance and richness in a degraded Afromontane forest of Kenya

In recent years, there have been considerable efforts to restore degraded tropical montane forests through active restoration using indigenous tree species. However, little is known about how these species used for restoration influence other species. In this study, two potential restoration species, Albizia gummifera and Neoboutonia macrocalyx, are investigated with regard to the relationship between their density and the abundance and richness of other plant species. The study was conducted in a degraded forest consisting of disturbed transition zones and secondary forest. Our results show positive relationships between the density of A. gummifera and the abundance of tree seedling and sapling richness in the transition zones and in the secondary forest. Shrub richness was negatively related to the density of A. gummifera. Abundance and richness of tree saplings and shrubs were positively related to N. macrocalyx density both in the transition zones and in the secondary forest. Herb species richness declined with N. macrocalyx density in the transition zones but increased with N. macrocalyx density in the secondary forest. The positive relationships between the density of the two tree species and species richness of other woody species suggest that both A. gummifera and N. macrocalyx can be suitable for active restoration of degraded mountain forests within their natural range.     

The hidden history of the snowshoe hare,Lepus americanus: extensive mitochondrial DNA introgression inferred from multilocus genetic variation

Hybridization drives the evolutionary trajectory of many species or local populations, and assessing the geographic extent and genetic impact of interspecific gene flow may provide invaluable clues to understand population divergence or the adaptive relevance of admixture. In North America, hares (Lepus spp.) are key species for ecosystem dynamics and their evolutionary history may have been affected by hybridization. Here we reconstructed the speciation history of the three most widespread hares in North America – the snowshoe hare (Lepus americanus), the white‐tailed jackrabbit (L. townsendii) and the black‐tailed jackrabbit (L. californicus) – by analysing sequence variation at eight nuclear markers and one mitochondrial DNA (mtDNA) locus (6240 bp; 94 specimens). A multilocus–multispecies coalescent‐based phylogeny suggests that L. americanus diverged ~2.7 Ma and that L. californicus and L. townsendii split more recently (~1.2 Ma). Within L. americanus, a deep history of cryptic divergence (~2.0 Ma) was inferred, which coincides with major speciation events in other North American species. While the isolation‐with‐migration model suggested that nuclear gene flow was generally rare or absent among species or major genetic groups, coalescent simulations of mtDNA divergence revealed historical mtDNA introgression from L. californicus into the Pacific Northwest populations of L. americanus. This finding marks a history of past reticulation between these species, which may have affected other parts of the genome and influence the adaptive potential of hares during climate change.