Las Cruces Biological Station

San Vito, Costa Rica

Las Cruces Biological Station

San Vito, Costa Rica
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Petelo M.,University of Hawaii at Manoa | Swierk L.,Las Cruces Biological Station | Swierk L.,Yale University
Integrative Zoology | Year: 2017

Whether or not sexually selected traits consistently exhibit positive allometry (i.e. are disproportionately large in larger individuals) is an ongoing debate. Multiple models and exceptions to this rule suggest that the underlying drivers of sexual trait allometry are nuanced. Here, we compare allometries of sexual and non-sexual traits of a species (Anolis aquaticus) within a well-studied lizard genus to test the competing hypotheses that sexual traits are, or are not, defined by positive allometry. We further consider the relationships of trait functions, which are relatively well understood in the genus Anolis, and allometry to identify potential drivers of allometric patterns. In particular, we explore how trait allometries interact to influence total organism function and generate sexual dimorphism. We quantified size (of targeted traits) and color of a sexual signal (the dewlap) in Anolis aquaticus in the field. The dewlap conveyed information relevant to intra-sexual combat and exhibited positive allometry. Overall, our results suggest that using single-trait allometries as indicators of past selection provides only an incomplete understanding of trait evolution. Although the function of positive allometry in some individual sexual signals (e.g. those conveying “super-honest” information) may be straightforward, we illustrate how scaling relationships interact synergistically to influence the function of phenotypes and propose avenues for future research. © 2016 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd

A study at the Las Cruces Biological Station in Costa Rica shows that when forests are linked by continuous corridors of trees, pollination has a greater likelihood of success. In contrast, when patches of forest are isolated from each other, pollinators are less abundant and plants frequently fail to reproduce. More than 94 percent of flowering tropical plants and 75 percent of the world's leading food crops require pollination by animals such as bees, bats and hummingbirds. Researchers have found that forest corridors enable specialized hummingbirds that prefer such landscapes to travel longer distances from one patch of trees to another, increasing pollen exchange between forest patches. Such patches not only harbor more hummingbirds but also display greater rates of pollination than plants in areas that are isolated from each other. These are among the results published today in the Proceedings of the Royal Society B, a technical journal, by scientists from the College of Forestry at Oregon State University and the Georg-August University Gottingen in Germany. "This work presents tropical forest landowners with a simple, relatively inexpensive solution to enhancing biodiversity and pollination of native forest plants—connect forest patches with hedgerows and wooded corridors," said Urs Kormann, the lead author of the study and a postdoctoral researcher at Oregon State. "This may complement national parks." "Wooded corridors remain abundant in many tropical landscapes," said Matthew Betts, co-author and assistant professor at Oregon State. "But as agricultural land use is expanding rapidly, quick action will be required to avert the disappearance of corridor elements between fragments. Otherwise, there may substantial losses of connectivity between forest remnants, leading to accelerated biodiversity loss." The researchers performed field experiments and conducted observations to arrive at their findings. They measured rates of hummingbird visits to feeders and to live plants (Heliconia tortuosa) placed in forest patches. They tracked the flow of pollen from one patch to another and evaluated the presence of two groups of hummingbird species, one that prefers forested habitats and one that does not. "Simple wooded corridors can boost landscape connectivity for pollinators and animal-pollinated plants," the researchers wrote. "Our findings may also apply to other organism groups that move along corridors, potentially providing other ecosystem services." Explore further: Beneficial plant 'spillover' effect seen from landscape corridors More information: Corridors restore animal-mediated pollination in fragmented tropical forest landscapes, Proceedings of the Royal Society B: Biological Sciences,

Mendenhall C.D.,Stanford University | Sekercioglu C.H.,University of Utah | Brenes F.O.,Las Cruces Biological Station | Ehrlich P.R.,Stanford University | Daily G.C.,Stanford University
Proceedings of the National Academy of Sciences of the United States of America | Year: 2011

Growing demand for food, fuel, and fiber is driving the intensification and expansion of agricultural land through a corresponding displacement of native woodland, savanna, and shrubland. In the wake of this displacement, it is clear that farmland can support biodiversity through preservation of important ecosystem elements at a fine scale. However, how much biodiversity can be sustained and with what tradeoffs for production are open questions. Using a well-studied tropical ecosystem in Costa Rica, we develop an empirically based model for quantifying the "wildlife- friendliness" of farmland for native birds. Some 80% of the 166 mist-netted species depend on fine-scale countryside forest elements (≤60-m-wide clusters of trees, typically of variable length and width) that weave through farmland along hilltops, valleys, rivers, roads, and property borders. Our model predicts with ∼75% accuracy the bird community composition of any part of the landscape. We find conservation value in small (≤20 m wide) clusters of trees and somewhat larger (≤60 m wide) forest remnants to provide substantial support for biodiversity beyond the borders of tropical forest reserves. Within the study area, forest elements on farms nearly double the effective size of the local forest reserve, providing seminatural habitats for bird species typically associated with the forest. Our findings provide a basis for estimating and sustaining biodiversity in farming systems through managing fine-scale ecosystem elements and, more broadly, informing ecosystem service analyses, biodiversity action plans, and regional land use strategies.

Ricardo K.,New York Botanical Garden | Oviedo-Brenes F.,Las Cruces Biological Station
Phytotaxa | Year: 2013

A new species of Miconia, M. povedae is described from a small remnant of primary forest at Las Cruces Biological Station in San Vito, Puntarenas province, Costa Rica. The new species is distinguished by its orangish indument of dendritic and stellate trichomes on most parts of the plant, sessile leaves with a tapering leaf base and strongly plinerved and asymmetric leaf venation, deflexed inflorescences, sessile herkogamous flowers with fused calyces that rupture at anthesis and geniculate staminal filaments. M. povedae is related to a group of for the most part Costa Rican and Panamanian endemics and the distinctive features of M. povedae and these species are discussed. Photographs of live plants, dissections of flowers preserved in ethanol, Scanning Electron Micrographs of leaf trichomes and a distribution map are provided. © 2013 Magnolia Press.

Lindell C.A.,Michigan State University | Cole R.J.,University of California at Santa Cruz | Cole R.J.,University of Hawaii at Manoa | Holl K.D.,University of California at Santa Cruz | Zahawi R.A.,Las Cruces Biological Station
Bird Conservation International | Year: 2012

Tropical land cover change has negatively affected numerous migratory bird populations. Forest restoration can augment migrant wintering habitat. However, almost no information exists about factors that influence migrant use of tropical restoration sites. We sampled migrant birds in young restoration sites in Costa Rica from February 2006 to April 2008 to determine how vegetation height, planting design, season, and landscape forest cover influenced capture rates of four declining species. We also documented total numbers of migratory species and individuals captured in each planting design treatment; each site had a control treatment where seedlings were not planted, an island treatment where seedlings were planted in patches, and a plantation treatment where seedlings were planted to cover the entire area. Sites varied in landscape forest cover within 500 m buffers. Three out of four focal species were captured significantly more often in plantation treatments than island or control treatments. Two of the four species showed seasonal patterns and one species was captured more often in high-vegetation sites. Greater numbers of species and individuals were captured in plantation treatments compared to island and control treatments. The plantation planting design increased migrant use more quickly than the island planting design. When resources are available, we recommend planting plantation-style to rapidly increase the value of restoration sites to a range of species, particularly those that use woody vegetation. When resources are more limited, planting islands may be a cost-effective, although not as ecologically effective, alternative that supports a diversity of migrant species compared to unplanted controls. © Copyright BirdLife International 2011.

Zahawi R.A.,Las Cruces Biological Station | Duran G.,National University of Costa Rica | Kormann U.,University of Gottingen
PLoS ONE | Year: 2015

Habitat loss and fragmentation of forests are among the biggest threats to biodiversity and associated ecosystem services in tropical landscapes. We use the vicinity of the Las Cruces Biological Station in southern Costa Rica as a regional case study to document seven decades of land-use change in one of the most intensively studied sites in the Neotropics. Though the premontane wet forest was largely intact in 1947, a wave of immigration in 1952 initiated rapid changes over a short period. Overall forest cover was reduced during each time interval analyzed (1947-1960, 1960-1980, 1980-1997, 1997-2014), although the vast majority of forest loss (>90%) occurred during the first two time intervals (1947-1960, 1960-1980) with an annual deforestation rate of 2.14% and 3.86%, respectively. The rate dropped to <2% thereafter and has been offset by forest recovery in fallow areas more recently, but overall forest cover has continued to decline. Approximately 27.9% of the study area is forested currently. Concomitantly, the region shifted from a single contiguous forest to a series of progressively smaller forest fragments with each successive survey. A strong reduction in the amount of core habitat was paralleled by an increased proportion of edge habitat, due to the irregular shape of many forest fragments. Structural connectivity, however, remains high, with an expansive network of > 100 km of linear strips of vegetation within a 3 km radius of the station, which may facilitate landscape-level movement for some species. Despite the extent of forest loss, a substantial number of regional landscape-level studies over the past two decades have demonstrated the persistence of many groups of organisms such as birds and mammals. Nonetheless, the continued decline in the quantity and quality of remaining habitat (~30%of remaining forest is secondary), as well as the threat of an extinction debt (or time lag in species loss), may result in the extirpation of additional species if more proactive conservation measures are not taken to reverse current trends-a pattern that reflects many other tropical regions the world over. © 2015 Zahawi et al.

Holl K.D.,University of California at Santa Cruz | Stout V.M.,University of California at Santa Cruz | Reid J.L.,University of California at Santa Cruz | Zahawi R.A.,Las Cruces Biological Station
Oecologia | Year: 2013

Restoring small-scale habitat heterogeneity in highly diverse systems, like tropical forests, is a conservation challenge and offers an excellent opportunity to test factors affecting community assembly. We investigated whether (1) the applied nucleation restoration strategy (planting tree islands) resulted in higher habitat heterogeneity than more homogeneous forest restoration approaches, (2) increased heterogeneity resulted in more diverse tree recruitment, and (3) the mean or coefficient of variation of habitat variables best explained tree recruitment. We measured soil nutrients, overstory and understory vegetation structure, and tree recruitment at six sites with three 5- to 7-year-old restoration treatments: control (no planting), planted tree islands, and conventional, mixed-species tree plantations. Canopy openness and soil base saturation were more variable in island treatments than in controls and plantations, whereas most soil nutrients had similar coefficients of variation across treatments, and bare ground was more variable in control plots. Seedling and sapling species density were equivalent in plantations and islands, and were substantially higher than in controls. Species spatial turnover, diversity, and richness were similar in island and plantation treatments. Mean canopy openness, rather than heterogeneity, explained the largest proportion of variance in species density. Our results show that, whereas canopy openness and soil base saturation are more heterogeneous with the applied nucleation restoration strategy, this pattern does not translate into greater tree diversity. The lack of a heterogeneity-diversity relationship is likely due to the fact that recruits respond more strongly to mean resource gradients than variability at this early stage in succession, and that seed dispersal limitation likely reduces the available species pool. Results show that planting tree islands facilitates tree recruitment to a similar degree as intensive plantation-style restoration strategies. © 2013 Springer-Verlag Berlin Heidelberg.

Cole R.J.,University of California at Santa Cruz | Holl K.D.,University of California at Santa Cruz | Zahawi R.A.,Las Cruces Biological Station
Ecological Applications | Year: 2010

Planting native tree seedlings is the predominant restoration strategy for accelerating forest succession on degraded lands. Planting tree "islands" is less costly and labor intensive than establishing larger plantations and simulates the nucleation process of succession. Assessing the role of island size in attracting seed dispersers, the potential of islands to expand through enhanced seed deposition, and the effect of planting arrangements on seed dispersal by birds and bats informs restoration design. Determining the relative importance of local restoration approach vs. landscape-level factors (amount of surrounding forest cover) helps prioritize methods and locations for restoration. We tested how three restoration approaches affect the arrival of forest seeds at 11 experimental sites spread across a gradient of surrounding forest cover in a 100-km2area of southern Costa Rica. Each site had three 50 X 50 m treatments: (1) control (natural regeneration), (2) island (planting tree seedlings in patches of three sizes: 16 m2, 64 m 2, and 144 m2), and (3) plantation (planting entire area). Four tree species were used in planting (Terminalia amazonia, Vochysia guatemalensis, Erythrina poeppigiana, and Inga edulis). Seed rain was measured for 18 months beginning ~2 years after planting. Plantations received the most zoochorous tree seeds (266.1 ± 64.5 seeds-m-2'yr-1 [mean ± SE]), islands were intermediate (210.4 ± 52.7 seeds.m -2yr-1), and controls were lowest (87.1 ± 13.9 seeds.m-2yr-1). Greater tree seed deposition in the plantations was due to birds (0.51 ± 0.18 seeds'm-2'd -1), not bats (0.07 ± 0.03 seeds-m-2'd -1). Seed rain was primarily smallseeded, early-successional species. Large and medium islands received twice as many zoochorous tree seeds as small islands and areas away from island edges, suggesting there is a minimum island size necessary to increase seed deposition and that seed rain outside of planted areas is strongly reduced. Planting design was more important for seed deposition than amount of forest cover within the surrounding 100- and 500-m radius areas. Establishing plantations and large islands facilitates the arrival of early-successional tree seeds and represents a broadly applicable strategy for increasing seed rain on abandoned agricultural lands. However, more intensive restoration approaches may be necessary for establishment of dispersal-limited species. © 2010 by the Ecological Society of America.

Zahawi R.A.,Las Cruces Biological Station | Holl K.D.,University of California at Santa Cruz | Cole R.J.,University of California at Santa Cruz | Cole R.J.,University of Colorado at Boulder | Reid J.L.,University of California at Santa Cruz
Journal of Applied Ecology | Year: 2013

Active forest restoration typically involves planting trees over large areas; this practice is costly, however, and establishing homogeneous plantations may favour the recruitment of a particular suite of species and strongly influence the successional trajectory. An alternative approach is to plant nuclei (islands) of trees to simulate the nucleation model of succession and accelerate natural recovery. We evaluated natural tree recruitment over 4 years in a restoration study replicated at eight former pasture sites in the tropical premontane forest zone of southern Costa Rica. At each site, two active restoration strategies were established in 50 × 50 m plots: planting trees throughout, and planting different-sized tree islands (4 × 4, 8 × 8, 12 × 12 m) within the plot. Restoration plots were compared to similar-sized controls undergoing passive restoration. Sites were spread across c. 100 km2 and distributed along a gradient of surrounding forest, allowing us to compare the relative importance of adjacent forest to that of within-site treatment on tree recruitment. Recruitment of animal-dispersed tree species was more than twofold higher in active (μ = 0·45 recruits m-2) as compared to passive restoration; recruitment was equivalent in plantation and island treatments, even though only 20% of the area in island plots was planted originally. The majority of recruits (>90%) represented early successional species (n = 54 species total). Density of animal-dispersed recruits was greater in large (0·80 ± 0·66 m-2) than small (0·28 ± 0·36 m-2) islands and intermediate in medium-sized islands. Seedling recruitment (<1 m tall) was greater in the interior of islands as compared to plantations, whereas sapling recruitment was similar, suggesting that island interiors may develop greater density of woody recruits as succession proceeds. Surrounding forest cover did not influence density or species richness of recruits among sites, although this factor may become more important over time. Synthesis and applications. Applied nucleation is a promising restoration strategy that can accelerate forest recovery to a similar degree as plantation-style restoration but is more economical. Appropriate island size is on the order of c. 100 m2. Practitioners should consider the methodology as an alternative to large-scale plantings. Applied nucleation is a promising restoration strategy that can accelerate forest recovery to a similar degree as plantation-style restoration but is more economical. Appropriate island size is on the order of c. 100 m2. Practitioners should consider the methodology as an alternative to large-scale plantings. © 2012 British Ecological Society.

Cole R.J.,University of California at Santa Cruz | Holl K.D.,University of California at Santa Cruz | Keene C.L.,Iowa State University | Zahawi R.A.,Las Cruces Biological Station
Forest Ecology and Management | Year: 2011

Natural regeneration of large-seeded, late-successional trees in fragmented tropical landscapes can be strongly limited by a lack of seed dispersal resulting in the need for more intensive restoration approaches, such as enrichment planting, to include these species in future forests. Direct seeding may be an alternative low-cost approach to planting nursery-raised tree seedlings, but there is minimal information on its efficacy or when in the successional process this technique will be most successful. We tested directly seeding five native tree species into habitats representing passive and active restoration approaches: (1) recently abandoned pasture; (2) naturally establishing, young secondary forests; and (3) young, mixed-species (fast-growing N-fixers and commercially valuable species) tree plantations established to facilitate montane forest recovery in southern Costa Rica. We monitored germination, survival, growth, and above- and below-ground biomass over a 2-year period. Germination in pastures, secondary forests, and tree plantations was similar (∼43%). Seedling survival after one and two years was significantly higher under tree plantations (91% year 1, 75% year 2) compared to secondary forests (76, 44%) or pastures (74, 41%). Moreover, seedlings had greater total biomass and lower root:shoot ratios in the plantations, suggesting higher nutrient availability in that treatment. Costs for direct seeding were 10- to 30-fold less per 100 seedlings after 2-year compared to nursery-raised seedlings planted at the same sites; however, there are important trade-offs to the two restoration approaches. Planting nursery-raised seedling is a more effective but higher cost approach for rapidly establishing canopy cover and restoring large areas whereas direct seeding is a more efficient way to enrich an existing system. We particularly recommend using direct seeding as a complimentary measure to the more intensive restoration approach of planting fast-growing and N-fixing trees. © 2010 Elsevier B.V.

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