Talamanca Cordillera Research Articles

Evidence for Caribbean plate subduction in southern Costa Rica

AbstractNestled between the Cocos, Nazca, Caribbean, and South American plates, the Panama microplate represents an area of rapidly evolving tectonics throughout the past ~10 m.y. Past and current studies have observed a notable amount of seismicity throughout this region, in particular the Caribbean coast of Costa Rica, which experienced a Mw 7.7 earthquake in 1991 CE. We investigated the crust and upper mantle structure of this region using the receiver function methodology and report two results: (1) first-order lateral constraints on the position of the Panama microplate boundary near the intersection between the Central Costa Rica Deformed Belt (onshore) and North Panama Deformed Belt (offshore), and (2) an impedance contrast south and east of these belts, supporting that the Caribbean plate currently subducts beneath the Panama microplate. Observed local seismicity is a consequence of the recently (ca. 14 Ma) initiated Caribbean plate subduction beneath the overlying Panama microplate. Our results are also consistent with a doubly convergent subduction margin dominating southern Costa Rica tectonics, uplifting the Talamanca Cordillera, and causing the cessation of southern Costa Rica volcanism over the past ~10 m.y.

Magmatic and Tectonic Domains of Central Costa Rica and the Irazú‐Turrialba Volcanic Complex Revealed by Ambient Noise Tomography

AbstractThe Central America Volcanic Arc runs from Guatemala to Panama, locally interrupted in Costa Rica after the twin‐system Irazú‐Turrialba Volcanic Complex, at the onset of the Talamanca Cordillera. A marked geological discontinuity characterizes the transition between the volcanic arc and this continental mountain range. To shed light on the spatial and structural relationships between active tectonics and volcanism, we deployed a temporary network consisting of 20 broadband seismic stations around the Irazú‐Turrialba Volcanic Complex that integrated the national seismic networks maintained by Costa Rican institutes. From the seismic records, we extract cross‐correlation functions and Rayleigh wave group‐velocity dispersion curves to perform two ambient noise tomographies at a regional and local scale. From this, we derive two models that point out the magmatic and tectonic features of the southern part of the Central American Volcanic Arc and of the Irazú‐Turrialba Volcanic Complex. The regional‐scale tomographic inversion suggests that such a volcanic complex shares a common reservoir at about 5–7 km depth that is fed by a sub‐vertical region, departing from at least 12 km depth. From here magmas appear to be transported upwards and stored in separate reservoirs below each volcanic edifice. Our study establishes an improved understanding of the spatial relationship between tectonic features and distribution of magmatic reservoirs underpinning the plumbing system of the Irazú‐Turrialba volcanic complex.

Arboreal camera trapping sheds light on seed dispersal of the world's only epiphytic gymnosperm: Zamia pseudoparasitica.

Epiphytic lifestyles have evolved independently in ecologically, morphologically, and taxonomically diverse plant species. Although this adaptation is widespread among angiosperms, it is only known to have arisen in a single gymnosperm species, Zamia pseudoparasitica (Cycadophyta). Zamia pseudoparasitica is endemic to the mountains of Western Panama, and little is known about the ecology of this unusual cycad. Here, we provide the first report of a potential seed disperser of Z. pseudoparasitica. Between late October 2019 and March 2020, we conducted arboreal camera trapping at three sites along the Talamanca Cordillera in Western Panama, yielding an accumulated survey effort of 271 camera days. Weekly direct observations were also performed using handheld binoculars at one site. Arboreal camera trapping revealed at least seven mammal species that visit this epiphytic cycad. At all three sites, the Northern olingo (Bassaricyon gabbii) was seen visiting individuals of Z. pseudoparasitica repeatedly, both while cones were closed and after they had opened. We estimated the time‐varying intensity of the visits throughout our sampling and used mixed models to compare the length of visits when cones were closed versus when they were open. Both duration and time‐varying intensity of visits increased after cones had opened and we documented Northern olingo removing and carrying away seeds. We also observed predation by the yellow‐eared toucanet (Selenidera spectabilis) which picked and destroyed mature Z. pseudoparasitica seeds. These results suggest that the Northern olingo could be an important seed dispersal agent for this rare epiphytic gymnosperm.

Altitude and community traits explain rain forest stand dynamics over a 2370‐m altitudinal gradient in Costa Rica

AbstractStand dynamic rates in Earth's vitally important tropical mountain rain forests are a central component of the response of these forests to global change, but their relationships to environmental gradients are poorly understood. We worked in mature forests on a 440–2810 m asl altitudinal gradient on Costa Rica's Talamanca Cordillera, making five censuses of 29 0.25‐ha permanent sample plots during 2012–2019. We determined mortality and recruitment rates, as well as basal area (G) increments, for individuals ≥10 cm diameter at breast height. Our main hypothesis was that stand dynamic rates decrease with altitude (therefore temperature); we also tested the hypotheses that rates increase with plot community‐weighted mean specific leaf area (CWM SLA) and decrease with CWM wood specific gravity (WSG). We developed regressions using generalized additive models to test our hypotheses. Mortality and recruitment rates decreased with altitude in line with our main hypothesis, though the strongly non‐linear mortality trend may be driven by extreme weather and temperature. Also, the best model for recruitment rates included plot CWM SLA with a negative relationship. Gross basal area increment ∆Ggross, the annual basal area increment of trees that survived the study period, had a hump‐shaped relationship to altitude, possibly related to the low CWM WSG of mid‐altitude forests. ∆Ggross was indeed negatively related to CWM WSG. However, net basal area growth (∆Gnet, the annualized difference between initial and final plot basal areas) was positively related to altitude due to low mortality in montane forests, in a model with CWM WSG with a negative relationship. ∆Gnet was negative in nine of the 29 plots at <1500 m asl. Patterns of rain forest stand dynamics on this long altitudinal gradient go beyond a direct response to temperature, and further work is required to improve scenarios of forest response to climate change. CWM traits should be measured to improve understanding. The effects of storms and lightning on low‐ and middle‐altitude forest and the potentially high resilience of montane Fagaceae‐dominated forests require attention. Diversity, not generality, should be expected on comparing tropical forest altitudinal transects.

Unravelling the genesis of young continental-arc shoshonites in the Talamanca Cordillera, Costa Rica

Six to five Myr. old continental-arc shoshonites and other high-K igneous rocks crop out among the summits of the Talamanca Cordillera, Central America. These rocks fill a previously assumed volcanic gap in eastern Costa Rica, showing that the Late Miocene-Pliocene magmatic arc was almost continuous along the current Talamanca Cordillera. Their trace element compositions (e.g., Sr ~ 1700 ppm at Rb ~ 120 ppm concentrations) together with fractional crystallization modeling, and isotopic signatures suggest a genesis related to subduction processes rather than lower crustal melting. Here we present a comprehensive geochemical study that integrates Monte Carlo simulations of trace element geochemistry and isotopic evidence in order to explain the origin of these highly enriched igneous rocks. The trace element budget of the Talamanca arc rocks requires the input of an incompatible element-enriched component, similar in composition to the Cocos Island Province (Pacific Ocean). We interpret the presence of this component to be the result of slab melting of subducted seamounts. Our model suggests that in southern Central America, contribution of OIB-related seamounts is a critical step for the generation of continental crust-like rock compositions.

Circadian activity patterns of mammalian predators and prey in Costa Rica.

Temporal niche shifts can shape predator–prey interactions by enabling predator avoidance, enhancing feeding success, and reducing competition among predators. Using a community-based conservation approach, we investigated temporal niche partitioning of mammalian predators and prey across 12 long-term camera trap surveys in the Pacific slope and Talamanca Cordillera of Costa Rica. Temporal overlap and segregation were investigated between predator–prey and predator–predator pairs using overlap analysis, circular statistics, and relative abundance after accounting for differences in habitat, season, and human impact among sites. We made the assumption that predators select abundant prey and adjust their activity to maximize their temporal overlap, thus we predicted that abundant prey with high overlap would be preferred prey species for that predator. We also predicted that similar-sized pairs of predator species with the greatest potential for competitive interactions would have the highest temporal segregation. Our results supported the existence of temporal niche separation among the eight species of predators—the smaller Leopardus felids (ocelot, margay, oncilla) were primarily nocturnal, the largest felids (jaguar and puma) and coyote were cathemeral, and the smaller jaguarundi and tayra were mostly diurnal. Most prey species (67%) were primarily nocturnal versus diurnal or cathemeral (33%). Hierarchical clustering identified relationships among species with the most similar activity patterns. We discuss the primary prey and competitor species predicted for each of the eight predators. Contrary to our prediction, the activity pattern of similar-sized intraguild competitors overlapped more than dissimilar-sized competitors, suggesting that similar-sized predators are hunting the same prey at the same time. From this we conclude that prey availability is more important than competition in determining circadian activity patterns of Neotropical predators. Our results indicate the presence of a delicate balance of tropical food webs that may be disrupted by overhunting, leading to a depauperate community consisting of ubiquitous generalists and endangered specialists. With Central America a hotspot for hunting-induced “empty forests,” community-based conservation approaches may offer the best road to reduce illegal hunting and maintain the biodiversity and community structure of tropical forest systems.

The Record of the Transition From an Oceanic Arc to a Young Continent in the Talamanca Cordillera

AbstractThe Talamanca Cordillera in the Central America Arc (Costa Rica‐Panama) preserves the record of the geochemical evolution from an intraoceanic arc to a juvenile continental arc in an active subduction zone, making it a testbed to explore processes that resulted in juvenile continental crust formation and explore potential mechanisms of early continental crust generation. Here we present a comprehensive set of geochronological, geochemical, and petrological data from the Talamanca Cordillera that tracks the key turning point (12–8 Ma) from the evolution of an oceanic arc depleted in incompatible elements to a juvenile continent. Most plutonic rocks from this transition and postintrusive rocks share striking similarities with average upper continental crust and Archean tonalite, trondhjemite, and granodiorite. We complement these data with seismic studies across the arc. Seismic velocities within the Caribbean Plate (basement of the arc) show a relatively uniform lateral structure consistent with a thick mafic large igneous province. Comparisons of seismic velocity profiles in the middle and lower crust beneath the active arc and remnant Miocene arc suggest a transition toward more felsic compositions as the volcanic center migrated toward the location of the modern arc. Seismic velocities along the modern arc in Costa Rica compared with other active arcs and average continental crust suggest an intermediate composition beneath the active arc in Costa Rica closer to average crust. Our geochemical modeling and radiogenic isotopes systematics suggest that input components from melting of the subducting Galapagos hotspot tracks are required for this compositional change.

Drivers of tropical rainforest composition and alpha diversity patterns over a 2,520 m altitudinal gradient.

AimWe sought to determine the relationship of forest composition and alpha diversity (the species diversity of a local assemblage) to altitude, soil, and spatial factors over a 440–2,950 m a.s.l gradient.LocationAltitudinal gradient on the Caribbean slope of the Talamanca Cordillera, Costa Rica.TaxonAngiosperm and gymnosperm trees, palms, and tree ferns.MethodsWe measured and identified all stems ≥10 cm dbh in 32 0.25‐ha undisturbed rain forest plots over the gradient. We determined compositional patterns using Non‐Metric Multidimensional Scaling (NMS) ordination, and used linear regressions to explore the relationship between four alpha diversity metrics and altitude. With variation partitioning (VARPART), we determined the compositional variation explained by altitude, soil, and spatial variables quantified using Principle Components of Neighbor matrices.ResultsWe identified 425 species. NMS axis 1 separated a lowland zone (440–1,120 m asl) from a transitional one dominated by holarctic Oreomunnea mexicana (1,400–1,600 m asl) and Quercus‐dominated forests at altitudes >2,100 m asl. The lowland zone was separated into two clusters of plots on NMS axis 2, the first in the 430–620 m asl range and the second at 1,000–1,120 masl. Regressions showed that all alpha diversity metrics were strongly negatively related to altitude (R 2 > 0.78). Overall, adjusted R 2 from VARPART was 0.43, with 0.30, 0.21, and 0.17 for altitude, soil, and space respectively. The respective adjusted R 2 of individual matrices, on controlling for the other two, was 0.06, 0.05 and 0.09 (p < 0.001).Main conclusionsThere are two well‐defined forest compositional zones on this gradient—lowlands 430–1,120 m asl and montane forests >2,150 m asl—with a transitional zone at 1,400–1,600 m asl, where lowland tropical and montane holarctic species are found together. Montane forests are very distinct in their composition and low alpha diversity. Vegetation and soil respond to altitude, and therefore temperature, as an integrated system, a model that goes beyond niche assembly as shown by the significant effect of space in the VARPART.

The Record of the Transition From an Oceanic Arc to a Young Continent in the Talamanca Cordillera

The Record of the Transition From an Oceanic Arc to a Young Continent in the Talamanca Cordillera

Deep divergence of Red-crowned Ant Tanager (Habia rubica: Cardinalidae), a multilocus phylogenetic analysis with emphasis in Mesoamerica.

Many neotropical species have a complex history of diversification as a result of the influence of geographical, ecological, climatic, and geological factors that determine the distribution of populations within a lineage. Phylogeography identifies such populations, determines their geographic distributions, and quantifies the degree of genetic divergence. In this work we explored the genetic structure of Habia rubica populations, a polytypic taxon with 17 subspecies described, in order to obtain hypotheses about their evolutionary history and processes of diversification. We undertook multilocus analyses using sequences of five molecular markers (ND2, ACOI-I9, MUSK, FGB-I5 and ODC), and sampling from across the species’ distribution range, an area encompassing from Central Mexico throughout much of South America. With these data, we obtained a robust phylogenetic hypothesis, a species delimitation analysis, and estimates of divergence times for these lineages. The phylogenetic hypothesis of concatenated molecular markers shows that H. rubica can be divided in three main clades: the first includes Mexican Pacific coast populations, the second is formed by population from east of Mexico to Panama and the third comprises the South American populations. Within these clades we recognize seven principal phylogroups whose limits have a clear correspondence with important geographical discontinuities including the Isthmus of Tehuantepec in southern Mexico, the Talamanca Cordillera, and the Isthmus of Panama in North America. In South America, we observed a marked separation of two phylogroups that include the populations that inhabit mesic forests in western and central South America (Amazon Forest) and those inhabiting the seasonal forest from the eastern and northern regions of the South America (Atlantic Forest). These areas are separated by an intervening dry vegetation “diagonal” (Chaco, Cerrado and Caatinga). The geographic and genetic structure of these phylogroups describes a history of diversification more active and complex in the northern distribution of this species, producing at least seven well-supported lineages that could be considered species.

El Sistema de Falla Navarro: desplazamientos izquierdos a lo largo del Cinturón Deformado del Centro de Costa Rica

En este estudio se define el sistema de falla Navarro con base en observaciones geológicas, geomorfológicas y sismológicas. Este sistema de falla está localizado entre las estribaciones norte de la cordillera de Talamanca y las faldas sur y sureste de los volcanes Irazú y Turrialba y está caracterizado principalmente por desplazamientos de tipo sinestral. El sistema de falla Navarro tiene un rumbo entre este-oeste y noreste-suroeste e incluye los segmentos denominados: Tarrazú, Navarro, Cachí, Urasca, Paraíso y Maravilla. Dos estructuras transtensivas denominadas Estrella y Ujarrás están presentes a lo largo del sistema de falla. Sismos en el periodo 1973-2015 fueron relocalizados iluminando las fallas del sector suroeste del sistema. Los mecanismos focales calculados corresponden en su mayoría con fallas de desplazamiento de rumbo en concordancia con las observaciones morfotectónicas.

Geographic isolation drives divergence of uncorrelated genetic and song variation in the Ruddy-capped Nightingale-Thrush (Catharus frantzii; Aves: Turdidae).

Montane barriers influence the evolutionary history of lineages by promoting isolation of populations. The effects of these historical processes are evident in patterns of differentiation among extant populations, which are often expressed as genetic and behavioral variation between populations. We investigated the effects of geographic barriers on the evolutionary history of a Mesoamerican bird by studying patterns of genetic and vocal variation in the Ruddy-capped Nightingale-Thrush (Turdidae: Catharus frantzii), a non-migratory oscine bird that inhabits montane forests from central Mexico to Panama. We reconstructed the phylogeographic history and estimated divergence times between populations using Bayesian and maximum likelihood methods. We found strong support for the existence of four mitochondrial lineages of C. frantzii corresponding to isolated mountain ranges: Sierra Madre Oriental; Sierra Madre del Sur; the highlands of Chiapas, Guatemala, and El Salvador; and the Talamanca Cordillera. Vocal features in C. frantzii were highly variable among the four observed clades, but vocal variation and genetic variation were uncorrelated. Song variation in C. frantzii suggests that sexual selection and cultural drift could be important factors driving song differentiation in C. frantzii.

Las fallas Purires y Picagres, y su relación con la secuencia sísmica del Puriscal de 1990

New morphotectonic, structural, and seismological interpretations have allowed us to define the neotectonics of the region located between the northwestern border of the Talamanca cordillera and the southern flanks of Aguacate Mounts, along the central-western sector of the Central Costa Rican Deformed Belt. The principal tectonic structures identified in this study are the Purires, Zapote, Jaris, Bajos de Jorco and Picagres faults. They constitute a set of northwest dextral-slip faults, traversing for more than 45 km the previous mountains ranges. Transtensive and transpressive structures were identified along these faults. Another recognized structure is the Junquillo fault, a predominantly east-west sinistral fault that lies between the Purires and Picagres faults.The three stages of the 1990 Puriscal shallow seismic sequence are reviewed in this study and are related with some of the previous faults. The seismic activity began with a seismic swarm that showed a peak of activity between May and June. The swarm showed a migration of activity between the Picagres and Purires faults. A right-lateral surface fault rupture with a length of 400 m, associated with two seismic events occurred on June 8 (00:31 GMT; Md 4.8) and June 9 (00:34 GMT; Md 4.8), breaks a sector of the eastern branch of Charcon transtensive structure of the Picagres fault. The seismic sequence continued with the Barbacoas earthquake of June 30 (Ms 5.1). This earthquake and its aftershocks located until July 11, rupture a 9 km length segment of the Purires fault. Finally, the Piedras Negras earthquake of December 22, 1990 (Ms 5.7) and its aftershocks occurred until December 30, caused a rupture of 11 km length of the Picagres fault.

Three New Species of &lt;I&gt;Dracontia&lt;/I&gt; (Pleurothallidinae, Orchidaceae) from Costa Rica

Three new species of Dracontia are described and illustrated from Costa Rica and comparisons with close relatives are made. A short discussion for the preference of describing them in Dracontia instead of Stelis is given. The three species are afterwards described: Dracontia montis-mortense, a species with a unique whitish lip with three purple stripes, which is found along the Pan-American Highway on the Cerro de la Muerte, and has been confused with Dracontia dracontea; Dracontia pileata, recognized by its hat-like dorsal sepal, and Dracontia viridi-flava, recognized by its all green-yellow flowers and erose lip. The latter species are both native to the south-Pacific watershed of the Talamanca Cordillera and closely related to Dracontia conochila and Dracontia hydra. A key to the Costa Rican species of Dracontia is given, accompanied by a discussion of the included species. Keywords—Dracontia montis-mortense, Dracontia pileata, Dracontia viridi-flava, Stelis, taxonomy. show a series of morphological features that are constant and are not part of the observed variation of other known species of the genus, suggesting reproductive isola- tion. Based on these observations, and taking into consider- ation that these entities are also geographically isolated from other similar species, they are described as different species herein.

The Limón, Costa Rica earthquake of April 22, 1991: Back arc thrusting and collisional tectonics in a subduction environment

On April 22, 1991, a large earthquake (Mw = 7.7) occurred along the Caribbean coast of Costa Rica and western Panama. The rupture area of the fault mapped from the aftershocks is 45×85 km2;. The distribution of aftershocks and the local geological record suggest that faulting occurred on a blind thrust sheet that shallows toward the northeast. Uplift of the Caribbean coast ranging from 1.5 m near Puerto Limón and decreasing gradually toward the southeast was observed along the Caribbean. Northwest of Puerto Limón no significant coastal uplift was observed. This observation agrees with the aftershock data suggesting the rupture did not extend to the northwest of this location. The Limón earthquake also triggered aftershocks on secondary faults in the crust. These events are apparently associated with a family of imbricate thrust and strike‐slip faults that lie in the eastern piedmont of the Talamanca Cordillera. The historical seismicity indicates that the Caribbean coast has been the site of several historical earthquakes with magnitudes greater than 7.0. On April 26, 1916, another earthquake (Ms = 6.9) took place in the same region. Summing the scalar seismic moment release along the Caribbean coast, the average rate of slip is approximately 0.8 cm/yr, compared with a value of 0.4 to 0.8 cm/yr along the Pacific subduction zone, depending on the estimated width of the seismogenic zone. Therefore a large fraction of the relative plate motion between the Cocos and Caribbean plates (9.8 cm/yr) appears to be taken up by crustal deformation in the back arc. The tectonic regime in the area appears to be dominated by the collision of the buoyant Cocos ridge with the subduction zone. The absence of a Wadati‐Benioff zone where the Cocos ridge collides with the trench suggests the slab does not subduct beneath the Osa Peninsula; this is supported by the Pliocene gap of volcanism present in Costa Rica. Thus the predicted relative motion between the Cocos and Caribbean plates appears to be absorbed by a low rate of seismic moment release in the forearc and by a broad zone of active crustal shortening and underthrusting in the back arc. This type of tectonic deformation resembles more a collisional regime than a typical subduction zone environment.