Danny E. Carvajal

The ecology, distribution and conservation status of Myrcianthes coquimbensis: a globally endangered endemic shrub of the Chilean Coastal Desert

Background: Myrcianthes coquimbensis is an endangered shrub endemic to Chile. No published account is known about its biology, ecology or threats to its continued existence. Aims: To document the current state of knowledge of M. coquimbensis regarding its geographic distribution, and population and reproductive parameters, and to evaluate threats in its distribution range. Methods: Historical records and recent survey data of 110 localities were used to characterise its known distribution. Plots were established in seven localities to determine the proportion of flowering individuals, recruitment and estimate population size and structure. Finally, levels of post-dispersal seed predation were determined in one locality. Results: The current distribution of M. coquimbensis extends along 82.8 km of the Chilean coast, where the species is mainly threatened by habitat loss. Only 13% of the individuals flowered during 2010, and 66% of these plants lost their entire flower crop due to desiccation. Few seeds (7.5%) were lost to post-dispersal seed predation. The populations are composed mainly of adult plants (70% of the individuals), and little to no recruitment was observed. Conclusions: M. coquimbensis populations are threatened by habitat loss and are not naturally recruiting through sexual reproduction. This exemplifies a case where studies on the ecology of a species are urgently needed to be able to design effective conservation and management plans.

Seed predation by rodents results in directed dispersal of viable seed fragments of an endangered desert shrub

Seed predation and seed dispersal are important ecological processes with antagonistic effects on plant recruitment. In the southern edge of the Atacama Desert in Chile, Myrcianthes coquimbensis is an endangered, large-seeded, vertebrate-dispersed shrub that in the present-day has no known dispersers. Native rodents hoard and eat the seeds of M. coquimbensis but leave viable seed fragments at the hoarding sites; soil interspaces within rock outcrops where seedlings recruit. Here we examined whether rodents act as effective dispersers of M. coquimbensis by discarding viable seed fragments in sites suitable for recruitment. We simulated different levels of endosperm loss to determine if seedlings could develop from seed fragments. We assessed how frequently rodents discarded fragments, and the probability that these fragments produced seedlings. Finally, we compared emergence and seedling survival at the hoarding sites and in two other habitats where seeds arrive to evaluate the suitability of the hoarding sites. Seeds of M. coquimbensis developed seedlings even after 87% of their storage tissue was removed. Rodents left seed fragments in more than 50% of the trials; almost 60% of the discarded fragments produced seedlings. Seedlings did not emerge from open ground habitats, and emergence was higher under M. coquimbensis shrubs than in rock habitats. Survival of two-year-old seedlings was higher in rock habitats than under conspecific adult shrubs. Our results suggest that rodents may play a dual role in the recruitment dynamics of M. coquimbensis, acting simultaneously as seed predators and effective dispersers. Therefore, though seed predators impose costs, their net effect on plant fitness in this system—where dispersers of large-seeded species have been lost—is likely positive.

Contrasting responses to water-deficit among Encelia canescens populations distributed along an aridity gradient

PREMISE OF THE STUDY Drought is the most limiting factor for plant growth and recruitment in arid environments. For widespread species, however, plant responses to drought can vary across populations because environmental conditions can vary along the range of the species. Here, we assessed whether plants of Encelia canescens from different populations along an aridity gradient in the Atacama Desert respond differently to water-deficit conditions. METHODS We conducted a common-garden experiment using plants grown from seeds from three populations distributed along an aridity gradient to test for differences in relative growth rate (RGR), biomass, root to shoot ratios, and photosynthesis between watered and water-deficit plants. Additionally, we examined the relationship between root to shoot ratios with RGR and total plant biomass along the gradient. KEY RESULTS Water deficit affected root to shoot ratios, biomass, and RGR, but not photosynthesis. Populations varied in RGR and biomass; plants from the most arid population had higher RGRs, but lower biomass than those from the least arid population. In watered conditions, root to shoot ratios did not vary with RGR or biomass. Conversely, with the water deficit, root to shoot ratios were negatively and positively related to biomass and RGR, respectively. CONCLUSIONS Response to water deficit differed among E. canescens populations; plants from the lowest rainfall environment adjusted root to shoot ratios, which may have allowed for equal biomass production across treatments. In contrast, plants from the wettest population did not adjust root to shoot ratios, but were reduced in biomass. These morphological and physiological changes to water availability showed that populations can use different strategies to cope with water deficit.

Different photoprotective responses under drought conditions of two predominant Chilean swamp forest species

Myrceugenia exsucca (DC.) O. Berg (Myrtaceae) y Luma chequen (Molina) A. Gray (Myrtaceae) son dos especies predominantes de los bosques pantanosos en Chile. Estas especies presentan diferente distribucion a traves de un gradiente de humedad y de precipitaciones, siendo L. chequen mas comun que M. exsucca en lugares con menor humedad. En este trabajo se plantea la hipotesis que L. chequen presenta una mayor plasticidad que M. exsucca de los atributos involucrados en fotoproteccion bajo condiciones de sequia. Para comprobar esta hipotesis, individuos de ambas especies fueron expuestos a un tratamiento de sequia. Un grupo de individuos fue mantenido con riego exhibiendo un potencial hidrico () optimo de -0.58 y -0.73 MPa para M. exsucca y L. chequen, respectivamente. Otro grupo fue sometido a sequia, donde el disminuyo a -1.4 MPa ( D) para ambas especies. Se encontro una mayor correlacion entre el contenido relativo de agua (RWC) y para M. exsucca (r2= 0.74) que para L. chequen (r2= 0.46), indicando que M. exsucca experimento una mayor deshidratacion que L. chequen durante el tratamiento. Como atributos de funcionalidad del aparato fotosintetico el nivel de clorofilas y la fluorescencia de la clorofila a fueron estudiados en plantas de ambas especies. Los resultados muestran que L. chequen redujo el contenido total de clorofilas y la eficiencia maxima del PSII (Fv/Fm) relacionado con una disminucion de la captura energetica e incremento significativamente la disipacion termica (qN). Por otro lado, M. exsucca no mostro cambios en estos parametros, pero redujo significativamente el nivel de los procesos fotoquimicos (qL), indicando un desbalance energetico. Los resultados indican que M. exsucca posee una menor plasticidad que L. chequen bajo condiciones de sequia. Se cree que estas diferencias pueden ser cruciales en el periodo de establecimiento y pueden estar influenciando la limitada distribucion de M. exsucca en sitios con menor disponibilidad hidrica.

Conspecific plants are better ‘nurses’ than rocks: consistent results revealing intraspecific facilitation as a process that promotes establishment in a hyper-arid environment

In stressful environments, nurse elements, such as shrubs or rocks, facilitate plant recruitment by providing less severe environments for seed germination and seedling survival. As seedlings develop, however, they may compete for resources with their nurse when it is a plant instead of a rock. We examined the role of conspecific plants and rocks as nurses of an endangered Atacama-Desert shrub. Establishment was highest under conspecific plants, revealing that in stressful environments plants can facilitate establishment of their own species. Our study contrasts findings from other environments where recruitment is lowest near plants of the same species.

Germination, seedling performance, and root production after simulated partial seed predation of a threatened Atacama Desert shrub

BackgroundSeed loss to predators is a common phenomenon across plant communities and an important determinant of plant recruitment. Although seed predators commonly destroy the entire seed, partial seed consumption has been reported for many species; however, the degree to which seed mass loss affects germination dynamics and survival of new individuals has been poorly documented. We simulated seed damage in natural conditions to examine how different levels of cotyledonary reserve removal affect germination dynamics and seedling performance of Myrcianthes coquimbensis (Myrtaceae), a threatened Atacama Desert shrub. The experiment combined two levels of seed maturity with three levels of seed mass loss.ResultsRemoval of the cotyledon reserves and seed maturity negatively affected the odds and the temporality of seedling emergence; nonetheless, seedlings were able to emerge from seed fragments, of either mature or immature seeds, that lost up to 75% of their original mass. Removal of cotyledonary reserves had negative effects on seedling size but no effect on root:shoot ratios.ConclusionsOur findings indicate that the loss of cotyledonary reserves in M. coquimbensis seeds is not necessarily lethal. Moreover, we posit that tolerance to partial seed consumption is likely a key reproductive strategy, which enables recruitment in this species.

Ecophysiological responses to drought followed by re-watering of two native Chilean swamp forest plants: Myrceugenia exsucca (DC.) O. Berg and Luma chequen (Molina) A. Gray

Myrceugenia exsucca (DC.) O. Berg y Luma chequen (Molina) A. Gray son dos especies predominantes de Myrtaceae del bosque pantanoso que estan fuertemente amenazadas por la destruccion de su habitat. Los programas de conservacion incluyen la creacion de nuevas areas protegidas que a menudo tienen diferentes condiciones ambientales respecto a su habitat natural. La tolerancia a la sequia y la capacidad de recuperacion son caracteristicas de gran importancia en los programas de conservacion en este tipo de plantas. Entender como estas plantas responden a la sequia y la rehidratacion fue el objetivo principal de este trabajo. Por ende, se estudiaron las relaciones hidricas, azucares solubles, pigmentos y rendimiento del fotosistema II (PSII). En general, el estado hidrico de L. chequen fue menos afectado que el de M. exsucca. Esto fue consistente con el mayor mantenimiento del apagamiento fotoquimico en L. chequen respecto a M. exsucca. Ademas, L. chequen exhibio una recuperacion completa del potencial hidrico y de la maxima eficiencia PSII incrementando estadisticamente el apagamiento fotoquimico (qP), que podria relacionarse con el fuerte incremento en los azucares solubles, indicando una mayor recuperacion fotosintetica. En contraste, M. exsucca fue incapaz de recuperar su potencial hidrico y la proporcion de centros de reaccion del PSII abiertos bajo condiciones de rehidratacion indicando una menor capacidad de recuperacion. Estos resultados muestran diferentes capacidades para hacer frente y restablecer el funcionamiento fisiologico despues de un episodio de escasez hidrica entre estas dos plantas de pantano chilenas. Esperamos que estos resultados sean importantes para el exito y gestiones de programas re-vegetacion a favor de la conservacion.

Accumulation capacity of cadmium and copper and their effects on photosynthetic performance in Azolla filiculoides Lam. under induced rhizofiltration

This study evaluated the capacity of Azolla filiculoides to enhance heavy metal accumulation through the addition of different concentrations of cadmium (Cd) and copper (Cu), as ethylenediaminetetraacetic acid (EDTA) complexes, under hydroponic conditions. The physiological effect was determined by Photosynthetic efficiency (Fv/Fm) as an indicator of plant stress, and heavy metal content was measured with flame atomic absorption spectroscopy in the whole plants. The results obtained in rhizofiltration systems did not show an increase in accumulation when Cd-EDTA was added, but the Cu-EDTA increased the accumulation of Cu by plants. Although the Fv/Fm was decreased in all treatments, only the Cd-EDTA complex caused damage to photosystem II (PSII) activity, and that damage was critical. These results coincide with the higher toxicity of cadmium to plants; the quantity of cadmium in the plants, although small, was indeed harmful to them. The correlation analysis for both heavy metals coincides with the assumption that the heavy metals on leaf tissue affected the photosynthetic metabolism. This research makes a new contribution to the field by evaluating EDTA-induced Azolla rhizofiltration in aquatic systems, a departure from the majority of the literature on the topic, which examines EDTA in soil remediation. In future, further study is needed on the interactions of EDTA with other ions and the physiological consequences for different plant species.