Beyond habitat structure: Landscape heterogeneity explains the monito del monte (Dromiciops gliroides) occurrence and behavior at habitats dominated by exotic trees

Spatial aggregation patterns in four mistletoe species: ecological and environmental determinants

Plant spatial distribution is an important topic in ecology as it determines species coexistence and biodiversity dynamics. Usually, plants show clustered distributions in nature. Mistletoes are a good example of aggregated distributions, as they form dense aggregations due to several factors (availability of competent hosts, seed dispersal vectors, microclimate conditions). We analysed four native mistletoe species with divergent life histories and host ranges: Desmaria mutabilis and Tristerix corymbosus from the temperate rainforests of southern Chile; and Tristerix aphyllus and Tristerix verticillatus from the northern semi-desert zone. While T. corymbosus and T. verticillatus have a wide host range, T. aphyllus and D. mutabilis are specialists that can parasitize only a few plant species. We hypothesized that specialized species would be more aggregated due to ecological and environmental restrictions. We used heterogeneous Poisson models to quantify spatial aggregation. Three of the four mistletoe species were spatially clustered at both environments, with aggregation being stronger in the temperate rainforest of southern Chile and particularly in the host-specialist species. Our results suggest that environmental constraints are more important than ecological constraints (host range) in shaping mistletoe spatial structure. Mistletoe aggregated spatial distribution depends primarily on the environment that they inhabit, which conditions host spatial availability, and arrangement.

Effects of landscape configuration on the occurrence and abundance of an arboreal marsupial from the Valdivian rainforest

Background

Habitat fragmentation and degradation processes affect biodiversity by reducing habitat quantity and quality, with differential effects on the resident species. However, their consequences are not always noticeable as some ecological processes affected involve idiosyncratic responses among different animal groups. The Valdivian temperate rainforests of southern Chile are experiencing a rapid fragmentation and degradation process despite being a biodiversity hotspot. Deforestation is one of the main threats to these forests. There inhabits the arboreal marsupial Dromiciops gliroides, an iconic species from the Valdivian rainforest, it is the only extant representative of the ancient Microbiotheria order, and it is currently threatened by habitat loss. Here we tested the effects of habitat configuration on D. gliroides occurrence and abundance along 12 landscapes of southern Chile with different disturbance levels.

Methods

We estimated D. gliroides occurrence and abundance using camera traps and related those metrics with landscape configuration indices obtained from FRAGSTATS (i.e., forest %, connectivity, patch number, contiguity, and distance to the nearest patch) using Bayesian linear mixed models.

Results

We found that D. gliroides occurrence was not influenced by landscape configuration, while its abundance was positively influenced by forest contiguity.

Conclusions

Although this arboreal marsupial is present in disturbed forests, its restricted movement capabilities and high dependency on the forest three-dimensional structure may affect its long-term persistence. We urge to rethink native forest conservation and management policies to improve habitat connectivity with possible positive consequences for native fauna.

The ecology and evolution of the monito del monte, a relict species from the southern South America temperate forests

The arboreal marsupial monito del monte (genus Dromiciops, with two recognized species) is a paradigmatic mammal. It is the sole living representative of the order Microbiotheria, the ancestor lineage of Australian marsupials. Also, this marsupial is the unique frugivorous mammal in the temperate rainforest, being the main seed disperser of several endemic plants of this ecosystem, thus acting as keystone species. Dromiciops is also one of the few hibernating mammals in South America, spending half of the year in a physiological dormancy where metabolism is reduced to 10% of normal levels. This capacity to reduce energy expenditure in winter contrasts with the enormous energy turnover rate they experience in spring and summer. The unique life history strategies of this living Microbiotheria, characterized by an alternation of life in the slow and fast lanes, putatively represent ancestral traits that permitted these cold-adapted mammals to survive in this environment. Here, we describe the ecological role of this emblematic marsupial, summarizing the ecophysiology of hibernation and sociality, updated phylogeographic relationships, reproductive cycle, trophic relationships, mutualisms, conservation, and threats. This marsupial shows high densities, despite presenting slow reproductive rates, a paradox explained by the unique characteristics of its three-dimensional habitat. We finally suggest immediate actions to protect these species that may be threatened in the near future due to habitat destruction and climate change.

Intermediate levels of wood extraction may facilitate coexistence of an endemic arboreal marsupial and Indigenous communities

Land-use change is a major driver of biodiversity loss. Large-scale disturbances such as habitat loss, fragmentation and degradation are known to have negative consequences for native biota, but the effects of small-scale disturbances such as selective logging are less well known. We compared three sites with different regimes of selective logging performed by Indigenous communities in the South American temperate rainforest, to assess effects on the density and habitat selection patterns of the Near Threatened endemic arboreal marsupial Dromiciops gliroides. We used structured interviews to identify patterns of wood extraction, which was 0.22–2.55 m3 per ha per year. In the less disturbed site only two tree species were logged, in the intermediately disturbed sites eight species were logged at low intensity, and in the most disturbed site seven species were logged intensively. The site with intermediate disturbance had the highest fleshy-fruited plant diversity and fruit biomass values as a result of the proliferation of shade-intolerant plants. This site also had the highest density of D. gliroides. These findings are consistent with Connell's intermediate disturbance hypothesis, suggesting that coexistence of people with nature is possible if wood extraction volumes are moderate, increasing plant diversity. Indigenous communities have sustainably used natural resources for centuries, but current rates of land-use change are becoming a significant threat to both them and their natural resources.

Regional-scale variation on Dromiciops gliroides occurrence, abundance, and activity patterns along a habitat disturbance gradient

Habitat structure may have a significant influence on the occurrence, abundance, and activity patterns of forest mammals. However, anthropogenic habitat disturbance changes habitat structure, which may alter those patterns of activity. We assessed occurrence, relative abundance, and activity patterns of Dromiciops gliroides, an arboreal marsupial endemic to the temperate rainforests of southern South America, contrasting four forest conditions at a regional scale: old-growth, second-growth, and logged forests, and abandoned exotic plantations. We conducted a camera-trap assessment in two consecutive austral summers across most of the Chilean range of D. gliroides, and compared habitat structure along a disturbance gradient. All structural features assessed differed among forest conditions. Dromiciops gliroides was present in all forest conditions, but its abundance decreased and activity got narrower as disturbance increased, being significantly lower in the exotic plantations. Activity patterns were variable among forest conditions and months, and were significantly more restricted temporally at exotic plantations. Although D. gliroides is tolerant to habitat disturbance, we show that structural alteration results in lower abundances and narrower activity patterns.

Movement behavior of the Monito del monte (Dromiciops gliroides): new insights into the ecology of a unique marsupial

Background

Behavior and activity patterns largely determine animal’s fitness and their ecological roles. Those patterns depend on many factors, being body mass, sex and age the most relevant in mammals. Particularly, those factors altogether with environmental conditions could influence movement behavior of mammals that hibernate, such as the Monito del monte (Dromiciops gliroides).

Methods

To evaluate its movement behavior and activity we radio-tracked D. gliroides 12 individuals (8 females and 4 males, corresponding to 5 adults and 7 sub-adults) during the austral summer. With the estimated locations we estimated home ranges, core areas and their relationship with body mass. We also assessed movement speed during early (19:00 to 01:00 h), peak (01:00 to 03:00 h) and late (03:00 to 07:00 h) activity periods. This study was conducted at the San Martín experimental forest (Valdivia, southern Chile).

Results

Estimated home range areas were 1.04 ± 0.20 ha, and core areas were 0.27 ± 0.06 ha; we found no significant differences between males and females, nor between adults and sub-adults. Home range and core areas were independent of body mass in females but showed positive relationships in males. Core area overlap was larger between sub-adult and adult individuals (35%) than between adult males and females (13%). Average movement D. gliroides speed was 1.45 m/min, reaching its lowest value during the peak activity period (01:00 to 03:00 h), but being faster during early and late activity periods. Those speed differences may be related to travelling and foraging activities.

Conclusion

Home range and core areas estimated here showed a large variability, which can be related to environmental factors. Home range size was positively correlated with body mass on males but not on females. Also, lower movement speeds at the peak activity period suggest that D. gliroides concentrates feeding activities at this time. As D. gliroides disperses the seeds of at least 16 native plant species, its movement behavior also has important consequences at the community level.

The hidden costs of living in a transformed habitat: Ecological and evolutionary consequences in a tripartite mutualistic system with a keystone mistletoe

Land use change is one of the most important anthropogenic drivers of biodiversity loss. Nevertheless, the ecological and evolutionary consequences of habitat transformation remain less understood than those from habitat fragmentation. Transformed habitats are structurally simpler, altering species composition and their ecological interactions, potentially compromising gene flow and genetic diversity. We focused on a tripartite mutualistic system composed of a mistletoe (Tristerix corymbosus), its pollinator (Sephanoides sephaniodes) and its seed disperser (Dromiciops gliroides) to assess changes in their ecological and evolutionary dynamics as a result of habitat transformation. We used eight microsatellite markers to compare genetic diversity, relatedness and gene flow among five mistletoe groups inhabiting native and transformed habitats (abandoned Eucalyptus globulus plantations). We found that these groups were genetically structured, with greater allelic richness and genetic diversity in their native habitat. Also, we found higher relatedness among mistletoe individuals in transformed habitats, which varied as a function of the geographic distance among plants, probably as a result of larger resource availability, which influenced mutualist visitation rates. We did not find differences in the current migration patterns, which suggests that Tristerix corymbosus may be resilient to habitat transformation. Yet, its highly specialized interactions along with changes in its spatial configuration depict a more complex scenario, which probably impose a cost in terms of lower genetic diversity and increased relatedness that might compromise its long-term viability.