Natural Forest Communities Research Articles

Comparison of post-fire planted and natural dry semi-deciduous forest communities in Ghana

The planting of mixed indigenous tree species for reforestation has gained attention in conservation biology, because they allow the recruitment of other woody species to a site. This study compared the differences in tree species diversity, structure, and composition between secondary dry semi-deciduous forests on two previously burned sites; one site had been planted ten-years prior with mixed mahogany species, while the other naturally regenerated after the fire. Density, dominance, frequency and importance value index (IVI) as well as family important values index (FIV) were computed to evaluate the floristic composition. A variety of diversity measures were also employed to examine heterogeneity in each forest type. For both sites, the most abundant diameter-class was 5-10 cm and the most abundant height-class was 1- 10 m. The study recorded significant differences between the two sites with respect to nearly all the indices of species diversity (Simpson, P = 0.037; Shannon, P = 0.003 and species richness, P = 0.003) employed, with the exception of Pielou’s index of evenness (P = 0.06).The planted site recorded highest values for all the measures of species diversity. However, Sorensen’s similarity index between planted and natural regeneration sites was 0.703. Seventeen and five species respectively were found to be solely associated with the planted and natural regeneration sites. At both sites the four most dominant and abundant tree species which recorded highest importance value index (IVI) were Ficus exasperate, Terminalia superba, Morida lucida, and Antiaris toxicaria. The greatest family importance values (FVI) for both sites were for Moraceae and Fabaceae, especially its sub-family Mimosaceae. The paper concludes that, use of mixed indigenous tree species in restoration facilitate the recruitment of a diverse group of other native tree species. Key words: Native species, diversity index, restoration, African mahoganies, stand structure.

Cold Tolerance among Composting Earthworm Species to Evaluate Invasion Potential

Exotic earthworm species that have traditionally been used for composting are purportedly intolerant of low temperatures, which may explain why they are rarely found outside of compost bins in temperate zones of North America. In contrast, numerous exotic European earthworm species have invaded previously earthworm-free temperate forests of North America where they impact native forest communities and ecosystem processes. A European species, Dendrobaena veneta, has recently become prevalent in the vermicomposting and bait industries, and its European origins and anecdotal reports of cold tolerance suggest that this species has the potential to become established in northern climates outside of its native range. Here we compare the survivorship of traditionally used composting species (Eisenia fetida and Perionyx excavatus) to D. veneta, and to a well established invasive European earthworm species (Lumbricus rubellus) at a low temperature (1.5 C) and room temperature (18 C), as a means of assessing the invasiveness of these species. Additionally, we compared the effect of this cold temperature treatment on the number of hatchlings that emerged from E. fetida and D. veneta cocoons. Adult earthworms exhibited near-100% survival in the room-temperature treatment, but survivorship varied appreciably among species in the low-temperature treatment. Perionyx excavatus and E. fetida mortality was similar, and each was greater than that of D. veneta, which was similar to L. rubellus. Dendrobaena veneta cocoons produced more hatchlings than E. fetida overall, and the number of hatchlings decreased in the low-temperature treatment relative to the room-temperature treatment for both species. When temperature corrected hatching rates were examined, the number of hatchlings was still less in the low-temperature treatment relative to the room-temperature treatment, suggesting embryonic mortality and not simply slowed development. Collectively, these results suggest that D. veneta shows greater cold tolerance than E. fetida, a trait that may increase its success as an invader.

Plant functional traits suggest novel ecological strategy for an invasive shrub in an understorey woody plant community

Summary1. Understanding ecological strategies of invasive species relative to the entire native community is important in understanding and managing both the mechanisms and the potential impacts of invasion, but few studies have taken this approach.2. We utilize advances in plant ecology to compare functional traits of an invasive shrub species, autumn‐oliveElaeagnus umbellata, to those of the understorey native woody plant community in a southeast Michigan forest. We estimate species trait distributions for six leaf functional traits (specific leaf area, leaf laminar area, leaf dry matter content, leaf nitrogen content, leaf carbon: nitrogen ratio and delta15N) using a kernel estimator. We then use pairwise trait distance and overlaps to describe the ecological strategy of the invasive shrub relative to that of the native understorey woody plant community.3. The overlap of the invasive shrub’s trait distribution with those of the native species was found to be smaller than the overlap of a native shrub’s distribution with other native species, consistent with the empty niche hypothesis of invasion. However, the invasive species’ mean leaf functional trait values typically fall outside of the range of most native species’ mean trait values, suggesting the invasive shrub extends trait space for understorey individuals of the native woody plant community.4. The invasive shrub’s leaf trait values are characteristic of a sun‐demanding species, contradicting its presence in the shaded forest understorey community and its persistence in an empty niche. We propose that this novel use of leaf functional traits by the invasive shrub could indicate that the invasion is facilitated by additional mechanisms such as release from natural enemies, association with nitrogen‐fixing bacteria, use of an empty temporal niche (namely the light available to the understorey early in the growing season), bird dispersal or some synthesis of these factors.5. Synthesis and applications. This study develops plant functional trait theory by studying an invasive species within the context of the entire native woody plant community. The approach can improve our understanding of the potential mechanisms of an invasion event and suggest ecological consequences and related management strategies for the maintenance of native forest communities. Specifically, this study, along with known data on the invasive species, suggests aggressive management in sunny gap and edge habitat provides the best strategy for long‐term control.

Effects of gypsy moth establishment and dominance in native caterpillar communities of northern oak forests

AbstractLittle research has addressed the impacts of invasive-species establishment on native forest insect communities. Such information is lacking even for gypsy moth,Lymantria dispar(L.) (Lepidoptera: Erebidae), the most thoroughly studied invasive forest insect. We investigated the ecological impacts of gypsy moth on native species at sites in north-central Ontario, Canada, with and without significant histories of gypsy moth defoliation over a 2-year period. Patterns in native forest caterpillar communities are described using measures of species diversity and multivariate analysis. We documented a transition from low-level to dominant gypsy moth populations. Sites with different gypsy moth outbreak histories exhibited differences in rank-abundance distributions and dominance structures in the first year of the study; by the second year, gypsy moth was dominant at sites of both types irrespective of their previous defoliation history. Contrary to our predictions, we found that gypsy moth outbreak history had no significant effects on native caterpillar community diversity or structure. However, sites with currently high gypsy moth abundance demonstrated significant shifts in late-season caterpillar community structure. Our results suggest that observed community differences were due to the presence of a highly abundant folivore, and not to permanent shifts in the native community because of the introduction of an invasive species.

Cinnamomum-Ardisia Forest in Northern Florida

Abstract Native old-field pineland with hardwood undergrowth was replaced 42 years later by alien hardwood forest dominated by invasive species at Goodwood forest in Tallahassee, Florida. Cinnamomum camphora dominated the overstory and Ardisia crenata the undergrowth. Succession theory would have anticipated development to native southern mixed hardwood forest or a subset called magnolia-beech forest. The initial native old-field forest community, prior to alien colonization, was characterized mostly by Pinus taeda, Quercus nigra, Liquidambar styraciflua and other lowland trees that were not likely to persist indefinitely on uplands. These trees colonized abandoned fields on account of a dearth of seed sources for oak-hickory forest trees which occupied these well drained uplands in the 18th century. Oak-hickory forest had been removed in the 19th century to allow the cultivation of cotton, and there was no evidence that it would recover at Goodwood forest.

Influences of geology and land use on macroinvertebrate communities across the Motueka River catchment, New Zealand

The influences of geology and land use on macroinvertebrate communities were investigated in the Motueka River catchment, New Zealand. Comparisons of functional feeding groups, multivariate community composition and biotic indices (MCI, QMCI, %EPT) were made between native forest stream reaches that differed in subcatchment geology (ultramafic, hard sedimentary, granite, gravel, karst) and between stream reaches surrounded by different land uses (native forest, exotic forest and pasture) within two of these geologies (granite, gravel). Differences in invertebrate community density and taxon richness were greater across the three land uses in the same geology than among the five geologies. Macroinvertebrate communities in streams flowing through native forest had greater numbers of shredders, and higher MCI scores than pastoral streams. Exotic forest macroinvertebrate communities were similar to the native forest communities in granite geology, but distinct from both native and pastoral communities in sites with underlying gravel geology. The results demonstrate that there is potential for underlying geology to influence the magnitude of land use impacts on invertebrate communities. The geologies within a catchment should be accounted for when considering the consequences of land development on river and stream communities.

Spatial patterns of tree species richness in two temperate forests

Summary1. The relative contribution of external vs. internal clustering mechanisms for determining community structure and its manifestations has been the subject of a continuous debate, but few attempts have been made to examine their single and joint effects in a compound process model.2. In this study, we tested four a priori hypotheses on the relative importance of habitat heterogeneity (topography and soil) and internal clustering mechanisms such as dispersal limitation on the species–area relationship (SAR) in two fully mapped 25‐ha plots of temperate forests in the Changbaishan (CBS) Nature Reserve, China, and the Chequamegon‐Nicolet National Forest in Wisconsin, USA.3. We used the distance decay curve to test the generality of the results obtained for the SAR. To find out if the relative importance of internal and external clustering mechanisms changed with life stage, we conducted separate analyses for small, large and all trees.4. Model selection favoured the most complex hypothesis that assumed an influence of both habitat heterogeneity and internal clustering on SAR and the distance decay curve. For the CBS plot, which shows weak topographical structuring, models were consistent with data only if soil factors were included into assessment of habitat heterogeneity. At the Wabikon plot, we could not test soil variables, but inclusion of topographical variables substantially improved the fit of the distance decay curve.5. In general, the results of the SAR agreed with those of the distance decay curve, but the latter was sensitive to positive habitat‐mediated species associations. The SAR, but not distance decay, distinguished among competing hypotheses for the community of large trees at CBS, where species exhibited only weak clustering.6. Contrary to our expectations, we did not find substantial differences in the relative importance of internal and external clustering mechanisms with life stage.7. Synthesis. Our analysis of spatial community structure for two relatively diverse temperate forests revealed that the factors governing spatial community structure may not substantially differ from those in highly diverse tropical forests. This result adds to our understanding of the ecological processes underlying the spatial diversity structure in natural forest communities.

Molecular Characterization of Soil Bacterial Community in a Perhumid, Low Mountain Forest

Forest disturbance often results in changes in soil properties and microbial communities. In the present study, we characterized a soil bacterial community subjected to disturbance using 16S rRNA gene clone libraries. The community was from a disturbed broad-leaved, low mountain forest ecosystem at Huoshaoliao (HSL) located in northern Taiwan. This locality receives more than 4,000 mm annual precipitation, one of the highest precipitations in Taiwan. Based on the Shannon diversity index, Chao1 estimator, richness and rarefaction curve analysis, the bacterial community in HSL forest soils was more diverse than those previously investigated in natural and disturbed forest soils with colder or less humid weather conditions. Analysis of molecular variance also revealed that the bacterial community in disturbed soils significantly differed from natural forest soils. Most of the abundant operational taxonomic units (OTUs) in the disturbed soil community at HSL were less abundant or absent in other soils. The disturbances influenced the composition of bacterial communities in natural and disturbed forests and increased the diversity of the disturbed forest soil community. Furthermore, the warmer and humid weather conditions could also increase community diversity in HSL soils.

Arboreal composition changes following white-tailed deer restoration to urban park forests without off-trail park visitor trampling

Human trampling destroys seedlings and saplings without regard to species in urban park forests and the addition of deer browsing compounds the losses. The unexamined research question is: what is the effect of white deer browsing in the absence of human trampling? Radnor Lake State Natural Area, Nashville, TN, USA has been protected from off-pathway human transit since 1973 and white-tailed deer ( Odocoileus virginianus Zimmerman) were restored to the Natural Area in 1980. From 1976 to 2007, a plot with tagged trees in the mesic slope forest showed the tree population for 16 species decreased, two remained stable, and one increased. The pattern of increase for sugar maple ( Acer saccharum Marsh) was 57 new trees added but 46 trees were lost, which appears as a population increase from 1976 to 1996 and a decrease in 2007. In all five forest communities, the total tree stems per ha declined from 1974 to 2008. During the period 1994–2008, O. virginianus over browsing decimated the seedling population of all species and caused the total for stems per ha for saplings to become smaller than the total stems per ha for trees in each community except the ravine forest, which had the greatest loss of trees. The only consistent change in trees across the five communities when comparing 1974–2008 was the significant tree importance value increase for A. saccharum. The conflicting significant changes for major species, other than A. saccharum, across the Natural Area forest communities informs management for other urban park forests—browsing by O. virginianus results in increased numbers for trees and saplings in the communities the species are well adapted to grow and reproduce in and fewer trees and saplings in the communities with environmental conditions that are not well suited to the species.

Soil bacterial communities in native and regenerated perhumid montane forests

Forest management often results in changes in soil properties and microbial communities. In the present study, we characterized differences in soil bacterial communities caused by forest management practices using 16S ribosomal RNA (rRNA) gene clone libraries. The communities were from a disturbed Chamaecyparis (DCP) forest subjected to harvesting of snags and downed logs, a secondary Chamaecyparis (SCP) plantation subjected to harvesting of old-growth trees, and a secondary cedar plantation (SCD). These forests were compared to a nearby native Chamaecyparis (NCP) forest in a perhumid montane ecosystem. At this locality, the elevation is from 1500 to 2100 m a.s.l., the mean annual precipitation >4000 mm, the mean annual temperature about 12 °C, and the soil pH <4. The phyla Acidobacteria and Proteobacteria predominated among the three disturbed forest soil communities. Several diversity indices and rarefaction curves revealed that the diversity of the SCD community was higher than that of the DCP soils. The diversity of the SCP community was intermediate. The bacterial diversity of the NCP community was lower than communities in the three disturbed forest soils. Analysis of molecular variance revealed that the bacterial community in SCD soils significantly differed from those in the three Chamaecyparis forest soils. Some of the abundant operational taxonomic units (OTUs) significantly differed among the four forest soils. Compared to the three disturbed forest soil communities, the NCP community was dominated by Proteobacteria, which accounted for more than half of the community. These results suggest that the disturbance of forest harvesting and tree species conversion influence the composition of bacterial communities in natural and disturbed forests and increase the diversity of the disturbed forest soil community.

Successional process of Picea crassifolia forest after logging disturbance in semiarid mountains: A case study in the Qilian Mountains, northwestern China

Selective logging is the most widely employed method of commercial timber production in Asia, and its impact on forest structure, composition, and regeneration dynamics is considerable. However, the successional processes in forest communities after logging in semiarid mountains are poorly understood. To provide more information on these processes, we used data from tree rings, direct and indirect age determinations, and field measurements of stand structure to reconstruct the historical disturbance regime, stand development patterns, and successional processes in a natural Picea crassifolia forest community in the Qilian Mountains of northwestern China. The results showed that the density of P. crassifolia forest increased significantly after logging. The densities of second growth forests 30 and 70 years after logging disturbance had increased to 2874% and 294% of primary forest's density, respectively. Logging disturbance did not alter tree species composition of logged stands. However, the diversity of understory species changed significantly among the successional phases. Logging disturbance decreased the spatial heterogeneity of second growth forest. The spatial distributions of recruitment were affected by the location of the remaining trees. There was less recruitment near the remaining trees than near forest that had been cut. In addition, logging disturbance also induced a growth release for the trees on the sites sampled. Our results imply that the succession and regeneration of P. crassifolia forest may be improved if the remaining trees could be retained relative uniform distribution pattern, thinning or selective logging could be performed to height density, exotic shrubs could be removed or the shrubs cover could be reduced during the earlier successional stages.

Species–area relationships explained by the joint effects of dispersal limitation and habitat heterogeneity

Species-area relationships (SARs) characterize the spatial distribution of species diversity in community ecology, but the biological mechanisms underlying the SARs have not been fully explored. Here, we examined the roles of dispersal limitation and habitat heterogeneity in shaping SARs in two large-scale forest plots. One is a 24-ha subtropical forest in Gutianshan National Nature Reserve, China. The other is a 50-ha tropical rain forest in Barro Colorado Island, Panama. Spatial point pattern models were applied to investigate the contributions of dispersal and habitat heterogeneity and their interactions to the formation of the SARs in the two sites. The results showed that, although dispersal and habitat heterogeneity each could significantly contribute to the SARs, each alone was insufficient to explain the SARs. Their joint effects sufficiently explained the real SARs, suggesting that heterogeneous habitat and dispersal limitation are two predominant mechanisms for maintaining the spatial distributions of the species in these two forests. These results add to our understanding of the ecological processes underlying the spatial variation of SARs in natural forest communities.

Spatial patterns of bird community similarity: bird responses to landscape composition and configuration in the Atlantic forest

Studies dealing with community similarity are necessary to understand large scale ecological processes causing biodiversity loss and to improve landscape and regional planning. Here, we study landscape variables influencing patterns of community similarity in fragmented and continuous forest landscapes in the Atlantic forest of South America, isolating the effects of forest loss, fragmentation and patterns of land use. Using a grid design, we surveyed birds in 41 square cells of 100 km2 using the point count method. We used multivariate, regression analyses and lagged predictor autoregressive models to examine the relative influence of landscape variables on community similarity. Forest cover was the primary variable explaining patterns of bird community similarity. Similarity showed a sudden decline between 20 and 40% of forest cover. Patterns of land use had a second order effect; native bird communities were less affected by forest loss in landscapes dominated by tree plantations (the most suitable habitat for native species) than in landscapes dominated by annual crops or cattle pastures. The effects of fragmentation were inconclusive. The trade-off between local extinctions and the invasion of extra-regional species using recently created habitats is probably the mechanism generating the observed patterns of community similarity. Limiting forest loss to 30–40% of the landscape cover and improving the suitability of human-modified habitats will contribute to maintain the structure and composition of the native forest bird community in the Atlantic forest.

Floristic analysis of the evergreen broad-leaved forest community from Jiulianshan National Nature Reserve in Jiangxi Province, China

Floristic composition of the evergreen broad-leaved forest in Jiulianshan Mountain was analyzed based on field investigations and community ecology. The community is rich in species diversity, with 144 spermatophyte families including 379 genera and 647 species, in which there are 6 gymnosperm families including 8 genera and 9 species, 21 monocotyledon families including 77 genera and 116 species, and 117 dicotyledon families including 294 genera and 522 species. Dominant families of the flora are Fagaceae, Lauraceae, Aquifoliaceae, Rosaceae, Ternstroemiaceae, Theaceae, Rubiaceae, Moraceae and Euphoarbiaceae, most of which are of tropical & subtropical distribution. As for family systematic distribution, the ratio of tropical & subtropical to temperate genera is 100:62.8 in 142 genera of 16 families. As for generic distribution in field investigation data, the tropical & subtropical areal type accounts for the majority of genera, in which there are 205 genera belonging to the tropical & subtropical areal type, 131 genera belonging to the temperate areal type, 35 genera belonging to the cosmopolitan areal type and 8 genera belonging to the endemic-to-China areal type. The ratio of the tropical & subtropical to temperate genera was 100:63.9. Floristic composition of the evergreen forest community in Jiulianshan and the typical species of the zonal flora will provide a scientific foundation for stand rehabilitation and stand establishment approximating a natural evergreen broad-leaved forest community. This study also indicates that the sample data based on community research are valid and convenient for floristic and environmental analysis of the evergreen broad-leaved forest community from the Jiulianshan Mountain.

Population growth rate of a common understory herb decreases non-linearly across a gradient of deer herbivory

Overabundant white-tailed deer ( Odocoileus virginianus) are a significant management problem in North America that exerts unprecedented herbivory pressure on native understory forest communities. Conserving understory plant populations requires quantifying a sustainable level of deer herbivory. To date, most population projection models consider only deer presence and absence. To estimate population growth rate along a gradient of herbivory, we focused on Trillium grandiflorum because it is a common understory species and a bellwether of deer effects and forest decline . We used matrix population models, and employed both prospective and retrospective analyses using a regression life table response experiment (LTRE). Deer affect size, stage and population dynamics of T. grandiflorum. Because deer target flowering and large non-flowering stages of T. grandiflorum, these individuals do not produce seed in the year they are browsed and are more likely to regress in stage and size in the following growing season relative to non-browsed plants. Importantly, sustained high browse levels result in populations dominated by small, non-flowering individuals. Our LTRE revealed a significant negative and decelerating relationship between herbivory and λ. This non-linearity occurs at the highest herbivory levels because highly browsed populations become dominated by stages that deer do not consume and are thus buffered from rapid decline. However, population extinction is expected when herbivory is greater than the pivotal value of ∼15%. Our study demonstrates that levels of deer herbivory commonly experienced by forest understory perennials are sufficient to cause the loss of T. grandiflorum and likely other co-occurring palatable species.

Fungi and diseases — natural components of healthy forestsThis article is one of a collection of papers based on a presentation from the Stem and Shoot Fungal Pathogens and Parasitic Plants: the Values of Biological Diversity session of the XXII International Union of Forestry Research Organization World Congress meeting held in Brisbane, Queensland, Australia, in 2005.

Forest health is described and perceived in different ways by the general public, land owners, managers, politicians, and scientists, depending on their values and objectives. Native tree pathogens and diseases are often associated with negative impacts even though damage is limited or not widespread. Too often, the concepts of tree health and forest health are used interchangeably and are not related to scale. Similar to fire, occurrences of disease outbreaks focus on the negative effects. However, native pathogens often exist in equilibrium with natural forest communities so their critical ecological roles are not easily discernible. Examined holistically, native fungi and diseases, dead and dying trees, and the many complex ecological interactions among them provide valuable benefits that ultimately contribute to sustainable, healthy forest ecosystems.

Relationship between species richness and biomass on environmental gradient in natural forest communities on Mt. Xiaolongshan, northwest China

We analyzed the relationship between species richness and biomass in natural forest communities at two similar sites on Mt. Xiaolongshan, northwest China. At both sites, a wide range of tree layer biomass levels was available by local biomass estimation models. In order to identify underlying mechanism of the species richness-biomass relationship, we included different water resource levels and number of individuals in each plot in our analysis. We sampled 15 and 20 plots (20 m × 20 m), respectively, at both two sites. These plots were sampled equally on the sunny slope and the shady slope. Species richness, number of individuals of each species and diameter at breast height (DBH) as a substitute of biomass of tree layer were recorded in each sample. At one site, the relationship between species richness and biomass was significant on the sunny slope, and this relationship disappeared on the shady slope due to more environmental factors. The relations between species richness and number of individuals and between number of individuals and biomass paralleled the species richness-biomass relation on both slopes. The difference in number of individuals-biomass relationships on the sunny slope and the shady slope revealed “interspecific competitive exclusion” even though the species richness-biomass relationships were not hump-shaped. At the other site, species richness was not related to biomass or to number of individuals. Our study demonstrated the importance of environmental stress and succession of community in the understanding of species diversity-productivity patterns.

Evolution of soil microbial biomass in restoration process of Robinia pseudoacacia plantations in an eroded environment

Vegetation recovery is a key measure to improve ecosystems in the Loess Plateau in China. To understand the evolution of soil microorganisms in forest plantations in the hilly areas of the Loess Plateau, the soil microbial biomass, microbial respiration and physical and chemical properties of the soil of Robinia pseudoacacia plantations were studied. In this study, eight forest soils of different age classes were used to study the evolution of soil microbial biomass, while a farmland and a native forest community of Platycladus orientalis L. were chosen as controls. By measuring soil microbial biomass, metabolic quotient, and physical and chemical properties, it can be concluded that soil quality was improved steadily after planting. Soil microbial biomass of C, N and P (SMBC, SMBN and SMBP) increased significantly after 10 to 15 years of afforestation and vegetation recovery. A relatively stable state of soil microbial biomass was maintained in near-mature or mature plantations. There was an increase of soil microbial biomass appearing at the end of the mature stage. After 50 years of afforestation and vegetation recovery, compared with those in farmland, the soil microbial biomass of C, N and P increased by 213%, 201% and 83% respectively, but only accounting for 51%, 55% and 61% of the increase in P. orientalis forest. Microbial soil respiration was enhanced in the early stages, and then weakened in the later stage after restoration, which was different from the change of soil organic carbon. The metabolic quotient (qCO2) was significantly higher in the soils of the P. orientalis forest than that in farmland at the early restoration stage and then decreased rapidly. After 25 years of afforestation and vegetation recovery, qCO2 in soils of the R. pseudoacacia forest was lower than that in the farmland soil, and reached a minimum after 50 years, which was close to that of the P. orientalis forest. A significant relationship was found among soil microbial biomass, qCO2 and physical and chemical properties and restoration duration. Therefore, we conclude that it is possible to artificially improve the ecological environment and soil quality in the hilly area of the Loess Plateau; a long time, even more than 100 years, is needed to reach the climax of the present natural forest.

TAXONOMIC REVISION OF THE MECYCLOTHORAX BEETLES (COLEOPTERA: CARABIDAE, PSYDRINI) OF MOLOKAI, HAWAII AND RECOGNITION OF AREAS OF ENDEMISM ON KAMAKOU VOLCANO

Species of the genus Mecyclothorax Sharp, 1903 from the island of Molokai, Hawaii are taxonomically revised. The Molokai fauna constitutes 43 recognized species, 24 newly described: M. polhemusi, new species; M. dunbarorum, new species; M. impunctatus, new species; M. debiliceps, new species; M. convexus, new species; M. subsinuatus, new species; M. subater, new species; M. trisetifer, new species; M. annae, new species; M. joni, new species; M. lisae, new species; M. lissopterus, new species; M. arcuatus, new species; M. latus, new species; M. abax, new species, M. ewingi, new species; M. latissimus, new species; M. punctatostriatus, new species; M. flavolateralis, new species; M. obscurus, new species; M. comma, new species; M. stenolophinus, new species; M. granulatus, new species; and M. cymindoides, new species. Mecyclothorax quadratus Britton is newly synonymized with M. argutor (Sharp). Various species are congruently distributed on Kamakou Volcano, allowing recognition of two areas of endemism, one to the west encompassing Kamakou and Olokui peaks, the second to the east spanning the areas from Wailau and Puu Lua to Puu Ohelo and Kainalu Gulch. Representatives of several hypothesized species pairs mutually occupy the two areas of endemism adding rigor to definition of the areas. Whereas the western Kamakou-Olokui area of endemism encompasses the State of Hawaii's Puu Alii and Olokui Natural Area Reserves and the Kamakou Preserve of The Nature Conservancy of Hawaii, the eastern Wailau-Puu Ohelo area of endemism is not comprehensively managed for conservation. Twelve of the 14 species residing in the eastern area of endemism are newly described, indicating the preliminary state of knowledge regarding the fauna of this area. Of those 12 new species, 9 are geographically restricted to the eastern area. This level of endemic richness is proposed as a criterion that justifies establishment of a comprehensive conservation plan for eastern Molokai, thereby ensuring sustainability of its distinct native forest communities. Two of the species, M. lissopterus and M. arcuatus, are cryptic sibling species, diagnosable only by configurations of the male aedeagal median lobe and female bursa copulatrix. The magnitude of the male median lobe in the two species is positively associated with size of the bursa copulatrix in females of the two species. Aedeagal and bursal configurations do not vary infraspecifically. Available evidence points most parsimoniously to origin of derived states in one of these species via developmental changes in genitalic anlagen common to the sexes, differentially expressed in males and females. Such a mechanism assumes homologous transformation of the male aedeagal median lobe and female bursa copulatrix, and removes the need to invoke more complicated hypotheses involving sexual selection.

Experimental field comparison of native and non‐native maple seedlings: natural enemies, ecophysiology, growth and survival

Summary 1 Acer platanoides (Norway maple) is an important non-native invasive canopy tree in North American deciduous forests, where native species diversity and abundance are greatly reduced under its canopy. We conducted a field experiment in North American forests to compare planted seedlings of A. platanoides and Acer saccharum (sugar maple), a widespread, common native that, like A. platanoides, is shade tolerant. Over two growing seasons in three forests we compared multiple components of seedling success: damage from natural enemies, ecophysiology, growth and survival. We reasoned that equal or superior performance by A. platanoides relative to A. saccharum indicates seedling characteristics that support invasiveness, while inferior performance indicates potential barriers to invasion. 2 Acer platanoides seedlings produced more leaves and allocated more biomass to roots, A. saccharum had greater water use efficiency, and the two species exhibited similar photosynthesis and first-season mortality rates. Acer platanoides had greater winter survival and earlier spring leaf emergence, but second-season mortality rates were similar. 3 The success of A. platanoides seedlings was not due to escape from natural enemies, contrary to the enemy release hypothesis. Foliar insect herbivory and disease symptoms were similarly high for both native and non-native, and seedling biomass did not differ. Rather, A. platanoides compared well with A. saccharum because of its equivalent ability to photosynthesize in the low light herb layer, its higher leaf production and greater allocation to roots, and its lower winter mortality coupled with earlier spring emergence. Its only potential barrier to seedling establishment, relative to A. saccharum, was lower water use efficiency, which possibly could hinder its invasion into drier forests. 4 The spread of non-native canopy trees poses an especially serious problem for native forest communities, because canopy trees strongly influence species in all forest layers. Success at reaching the canopy depends on a tree's ecology in previous life-history stages, particularly as a vulnerable seedling, but little is known about seedling characteristics that promote non-native tree invasion. Experimental field comparison with ecologically successful native trees provides insight into why non-native trees succeed as seedlings, which is a necessary stage on their journey into the forest canopy.