Biology subjects

Carvajal, T.

Publications and source records attributed to Carvajal, T..

4 recordsLinked to original sources

bioRxiv2019

Unraveling the genetic structure of the coconut scale insect pest (Aspidiotus rigidus Reyne) outbreak populations in the Philippines

The Philippines suffered from a devastating outbreak of the coconut scale insect pest, Aspidiotus rigidus Reyne inflicting significant economic losses to the countrys coconut industry. Despite the massive outbreak, little is known about the population and dispersal history of this invasive pest in the Philippines. Here, we examined the genetic diversity, structure and demographic history of A. rigidus sampled from localities with reported outbreaks from 2014 to 2017. We analyzed the genetic structure of seven A. rigidus outbreak populations using mitochondrial COI and nuclear EF-1 markers. Both markers and all methods of population genetic structure analyses indicate clear differentiation among the A. rigidus populations separating the northern (i.e., Luzon provinces) from the southern (i.e., Basilan and Zamboanga Peninsula) regions of the Philippines. Very low or no genetic differentiation was observed within and amongst the populations per geographic region indicating two unrelated outbreak events of the pest originating from two genetically uniform populations isolated in each respective region. Historical data supports the resurgence of an established A. rigidus population in the south which could have been driven by sudden climatic changes or human-induced habitat imbalance. Given no historical information, we disregard the possible resurgence from the northern population and infer that the outbreak could have resulted from a recent introduction of a non-native A. rigidus in the region. Our study provides valuable information on the genetic differentiation of the two A. rigidus groups that would be useful for developing and implementing biological control strategies against this pest in the Philippines.

genetics↗

bioRxiv2019

Species dispersal mediates opposing influences of a branching network on genetic variation in a metapopulation

Aim Fractal networks, represented by branching complexity in rivers, are ubiquitous in nature. In rivers, the number of either distal (e.g., in headwater streams) or confluent (e.g., in mainstems) locations can be increased along with their branching complexity. Distal- or confluent-spatial locations can result in fewer or greater corridor linkages that can alter genetic divergence at the metapopulation scale. These mechanisms underlying the resulting genetic structuring remain poorly understood at the metapopulation scale, particularly in terms of the roles of species-specific dispersal traits. The objective of this study is to mechanistically understand how branching complexity can simultaneously influence genetic divergence in opposite directions.Location Northeastern JapanMethods To evaluate the integrated influences of network complexity and species dispersal on genetic divergence among populations at the catchment scale, we conducted simulation modelling on a mechanistic framework based on Bayesian inference by adapting empirical genetic data from four macroinvertebrate species. Simulations were then done using empirical and virtual species-characteristics on virtual river networks.Results Our novel simulation showed that both greater landscape connectivity (resulting from shorter watercourse distance) and greater isolation of distal locations occurred in the more-branched river networks. These two spatial features have negative and positive influences on genetic divergence, with their relative importance varying among different species and dispersal characteristics. Specifically, genetic divergence at the metapopulation scale increased for species having higher downstream-biased dispersal but decreased for species having higher upstream-biased dispersal. Distal populations (e.g., in headwaters) have higher genetic independence when downstream-biased asymmetry is higher.Main conclusions We found a strong association between species dispersal and evolutionary processes such as gene flow and genetic drift. This association mediates the pervasive influences of branching complexity on genetic-divergence in the metapopulation. It also highlights the importance of considering species dispersal-patterns when developing management strategies in the face of rapid environmental-change scenarios.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2018

Using Google Trends to Examine the Spatio-Temporal Incidence and Behavioral Patterns of Dengue Disease: A Case Study in Metropolitan Manila, Philippines

Dengue is a major public health concern and an economic burden in the Philippines. Despite the countrys improved dengue surveillance, it still suffers from various setbacks and therefore needs to be complemented with alternative approaches. Previous studies have demonstrated the potential of internet-based surveillance such as Google Dengue Trends (GDT) in supplementing current epidemiological methods for predicting future dengue outbreaks and patterns. With this, our study aims to assess the temporal relationship of GDT and dengue incidence in Metropolitan Manila from previous years and examine web search behavior of the population towards the disease. The study collated and organized the population statistics and reported dengue cases in Metropolitan Manila from respective government agencies to calculate the spatial and temporal dengue incidence. The relative search volume of the term dengue and top dengue-related search queries in Metropolitan Manila were obtained and organized from the Google trends platform. Data processing of GDT and dengue incidence was performed by conducting an adjustment procedure and subsequently used for correlation and cross-correlation analyses. Moreover, a thematic analysis was employed on the top dengue-related search queries. Results revealed a high temporal relationship between GDT and dengue incidence when either one of the variables is adjusted. Cross-correlation showed that there is delayed effect (1-2 weeks) of GDT to dengue incidence, demonstrating its potential in predicting future dengue outbreaks and patterns in Metropolitan Manila. Thematic analysis of dengue-related search queries indicated 5 categories namely; (a) dengue, (b) sign and symptoms of dengue, (c) treatment and prevention, (d) mosquito and (e) other diseases where the majority of the search queries was signs and symptoms which indicate the health-seeking behavior of the population towards the disease.

epidemiology↗

bioRxiv2018

DETECTION OF Wolbachia IN FIELD-COLLECTED MOSQUITO VECTOR, Aedes aegypti

It was the impression from past literature that Wolbachia is not naturally found in Ae. aegypti. However, there are have been reports that recently reveals the presence of this endosymbiont in this mosquito vector. With this, our study presents additional support of Wolbachia infection in Ae. aegypti by screening field-collected adult mosquitoes using Wolbachiaspecific 16S rDNA and its surface protein (wsp) makers under optimized PCR conditions. From a total of 672 Ae. aegpyti adult mosquito samples collected in Metropolitan Manila, Philippines, 113 (16.8%) and 89 (13.2%) individual mosquito samples were determined to be Wolbachia infected using the wsp and 16S rDNA markers, respectively. The Ae. aegpyti wsp sample sequences were similar or identical to five known Wolbachia strains belonging to supergroups A or B while majority of 16S rDNA sample sequences were similar to strains belonging to supergroup B. Overall, 80 (11.90%) individual mosquito samples revealed to show positive amplifications in both markers and 69.0% showed congruence in supergroup identification (supergroup B). Our findings illustrate that the infection status of Wolbachia in Ae. aegypti may appear common than previously recognized.

microbiology↗