OAR@UM Collection:

DNA barcoding and phylogenetics of selected hymenopteran species from Gozo

2023-03-21T10:52:30Z

Title: DNA barcoding and phylogenetics of selected hymenopteran species from Gozo Abstract: DNA barcoding and phylogenetic and morphological analyses have proven to be essential tools in correct species identification, especially for poorly studied taxa or taxa containing a high level of cryptic morphological diversity, such as those found in the order Hymenoptera. In this study, bees, wasps and sawflies (order Hymenoptera) were sampled during a total of 46 fieldwork sessions taking place in Gozo. A total of 179 specimens were morphologically identified down to the lowest taxon possible. Various ecological data, such as the hymenopterans sampled per habitat type, were also evaluated. DNA was extracted from all the sampled specimens during the genetic analyses, and a partial sequence of 658 bp from the cytochrome oxidase subunit 1 gene (COI) was amplified. PCR amplification was confirmed through gel electrophoresis. PCR products were sequenced, and the sequences generated were compared to publicly available data on BOLD and GenBank to confirm species identity. The 179 specimens were genetically confirmed to represent 59 species from 17 families belonging to 8 superfamilies within Hymenoptera. The genetic dataset compromising all the studied specimens was aligned and used to produce a phylogenetic tree using Bayesian Inference. Specimens from the same species grouped with high posterior probability values, confirming that they genetically belong to the same species. While locally some morphological studies focused on Hymenoptera, genetic work on this order for the Maltese Islands is minimal, whilst this is the first genetic study on hymenopterans from Gozo. Only 12% of the studied species were previously scientifically recorded from Gozo, including species such as Xylocopa violacea. Therefore this work contributes highly to the knowledge gap reduction for hymenopteran species in Gozo. Additionally, out of the 80 haplotypes recorded in this study, 42 novel haplotypes belonging to 35 out of 59 studied species were also discovered, further contributing to the genetic resources available on these species at an international level. This study also paves the way towards a better understanding of the conservation needs of identified bees, wasps, and sawflies. These species are increasingly recognised for their valuable ecological roles as pollinators or predators of pest insect species. Description: B.Sc. (Hons)(Melit.)

A predictive occurrence model for ‘Elatine gussonei’ based on environmental factors

2022-12-01T06:07:23Z

Title: A predictive occurrence model for ‘Elatine gussonei’ based on environmental factors Abstract: The occurrence of the amphibious plant Elatine gussonei in Mediterranean Temporary Ponds (EU priority habitat 3170* and Natura 2000 site) is patchy, with a strong stochastic component. The specific environmental conditions and tolerance ranges that determine its presence in a pool are not known. This represented the knowledge gap that this study aimed to address. The chemical, morphometric and ecological conditions in a sample of rockpools were collected and used to construct a preliminary occurrence model. Throughout this study, ca. 170 pools from 10 pool landscapes were surveyed from the Maltese Islands. Data collected and used in analyses included species lists, water quality (pH, Electrical Conductivity and Oxidation Reduction Potential), and basin morphometry (dimensions, surface area, maximum water and sediment depths of the basin and depths at which E. gussonei was present). Analyses carried out included correlation plots, CCA, RDA, t-tests, linear regressions (lm) and binomial logistic regressions (generalized linear models – glm). Elatine gussonei occurrence in the model was based on dichotomous presenceabsence data of the species. Therefore, binomial glms were carried out for environmental factors. Only zwm and surface area (both negatively correlated with occurrence) were statistically significant (p<0.05) and were used to model the species occurrence in a given pool. Once the presence of the species was confirmed via glm, lm were used to model the specific depths at which it occurs. The dependent depths (zwe and zse) were significantly positively correlated with independent maximum basin depths (zwm and zsm). Constraining the lms to pass through the origin, however, increased model efficiency by increasing R2 (0.54 to 0.72 and 0.44 to 0.84 for water and sediment depths), indicating better model fit. Literature states that its phenotypic plasticity and rapid response to environmental changes make it a good sentinel species on which to model climate change and predict further environmental changes and habitat status. The species and its habitat are both protected, entitling them to monitoring and conservation. Description: M.Sc.(Melit.)

A comparison of coastal plant trait variability between Maltese endemics and their widespread Mediterranean congeners

2022-04-19T05:45:01Z

Title: A comparison of coastal plant trait variability between Maltese endemics and their widespread Mediterranean congeners Abstract: Identifying the ecological characteristics of narrow endemic species is essential, not only for providing insight on the evolutionary patterns leading to endemism, but also for its contribution to establish guidelines for their conservation. The aim of this study was to investigate plant trait variability between congeneric pairs of endemic and widespread species from two wide ranging taxa, Limonium and Euphorbia, to identify any ecological characteristics unique to endemic species, hence identifying their patterns of endemism on the Maltese islands and, based on these traits, determine the extent of ecological impact associated with landscape modification. Sampling was carried out at 21 sites around the islands of Malta, Gozo and Comino. Environmental parameters related to stress were compared for each species, together with plant competitiveness including coexisting species and ecophysiological parameters pertaining to plant resource acquisition and conservation abilities established through functional leaf traits. Morphological and reproductive analyses including flower density, pollen viability and flower synchrony were similarly carried out for each species. Whilst for the endemic species investigated the ‘specialist’ model seems to be the most likely process leading to their endemism on the Maltese islands, PCA analyses highlighted that both endemic and widespread species correspondingly exhibit adaptations to withstand environmental constraints with the endemic species being not more stress tolerant than their widespread congeners. This, with the exhibition of a lower competitive capacity by endemics has clear implications on their persistence in a competitive environment. Results also demonstrated morphological variations between the congeneric pairs whereby certain morphological traits such as habit and branching angle are plastic, whilst other traits including leaf dimensions and corolla width are evolutionary products of endemism. Reproductive traits including higher flower densities, smaller flowers with less elaborate displays and limited pollen production reflected by a lower pollen viability are unique in endemics. These traits render selfing as the main breeding strategy adopted by endemics which serves as an obstacle for the evolution of adaptations in changing environments and hence raises implications for their long term survival on the Maltese islands. Description: M.Sc.(Melit.)

Factors influencing the abundance and distribution of feral pigeons (Columba livia) in urban environments in Malta

2022-04-19T05:41:53Z

Title: Factors influencing the abundance and distribution of feral pigeons (Columba livia) in urban environments in Malta Abstract: Feral pigeons (Columba livia) have long been regarded as a pest in urban environments. A key first step for effective pest control is to evaluate the population size. Apart from studying the abundance and distribution of the bird in selected urban environments on Malta, the present research aimed to investigate which, and how, urban environmental characteristics influence feral pigeon numbers. The tool used for this was Distance Sampling, a frequently used methodology for estimating animal density and/or abundance. Three towns from each district of mainland Malta were chosen. (Southern Harbour: Paola, Kalkara, Fgura; Northern Harbour: Msida, Swieqi, St Julians; South Eastern: Birzebbugia, Marsaskala, Marsaxlokk; Western: Iklin, Mtarfa, Rabat; Northern: St Paul’s Bay, Mgarr, Mellieha. Ten transects per town were then allocated along roads categorised in five urban environment types: (i) Local centres, (ii) Residential areas, (iii) Residential Priority Areas, (iv) Public open spaces within town, (v) Public open spaces at periphery. After a pilot study to select the transects, the actual study was implemented between May and August 2020. Fieldwork was carried out during weekdays only, from 8:00 till 12:00, to ensure consistency. Each transect was walked in one direction taking note of the frequency of occurrences of various urban environmental parameters on one side of the road and was then walked back on the other side of the road. The walking session was then repeated this time recording any feral pigeons present whilst measuring their perpendicular distance to the transect line using a laser rangefinder. The data were compiled into a matrix of feral pigeon abundance within the districts, localities and transect types. To test whether there was a correlation between the abundance of feral pigeons and urban environment characteristics, Generalized Linear models (GLM) were used, specifically the Negative Binomial Regression after first using the Spearman’s Rank-Order Correlation to check for multicollinearity. The abundance and density of the feral pigeon population in the urban setting was subsequently estimated using Distance Sampling Analysis. Significant differences in pigeon abundance was found between transect types paired up with either ‘Mainroad’ and ‘Park’, suggesting that they share features that attract pigeons. The Spearman’s Rank-Order Correlation indicated that there were various urban environmental variables that resulted as significant, however, ‘Old Buildings’ and ‘Modern Buildings’ were the two that had the highest correlation coefficient (0.507 and -0.420 respectively). Of a number of models tested, Model 6, which included only the predictor variable ‘Modern Buildings’, resulted as the best fitting, hence showing that ‘Modern buildings’ is an urban environmental characteristic that significantly and negatively affected the feral pigeon abundance, that is, feral pigeon abundance is low where modern buildings are predominant. The Distance Sampling Analysis showed that, the total abundance of feral pigeon clusters was estimated to be 293.89±70.87, each cluster having two or three pigeons, and with the ‘Mainroad’ transect type having the highest numbers of clusters, followed by ‘Park’, ‘Sidestreet’, ‘Agricultural area’ and ‘Suburb’ in this order. The highest estimate of cluster density of feral pigeons was for ‘Park’, followed by ‘Mainroad’, ‘Agricultural area’, ‘Sidestreet’ and ‘Suburb’, in this order. The present study demonstrates that urban characteristics do indeed influence the abundance and distribution of feral pigeons even if the birds travel long distances and have home ranges that include multiple habitat types. The present results can serve as a stepping stone for further research on feral pigeon populations and urban ecology in general. Description: M.Sc.(Melit.)