https://www.um.edu.mt/library/oar/handle/123456789/403 Wed, 03 Jun 2026 21:40:11 GMT 2026-06-03T21:40:11Z https://www.um.edu.mt/library/oar/handle/123456789/147019 Title: Analyzing ordinal categorical responses using multilevel models with an application related to dancing Authors: Camilleri, Liberato; Pellicano, Milena Abstract: Ordinal categorical outcomes frequently arise in applied research, particularly in settings where responses are recorded using rating scores rather than continuous measurements. In many practical applications, the data may be nested in higher level structures, with observations clustered within higher-level units, leading to dependence that cannot be adequately handled by standard regression models. This paper analyses ordinal categorical responses within a multilevel modelling framework, with particular emphasis on likelihood-based estimation methods for generalized mixed-effects models and their practical application to dance competition data. The study first develops the theoretical foundation of two-level models for ordinal responses assuming a multinomial distribution and a logit link function. Particular attention is given to random intercept and random coefficient structures, the interpretation of between-cluster variation, and the role of intra-class correlation in assessing dependence within hierarchical data. The paper then discusses the estimation and inferential techniques used for multilevel ordinal models and explores procedure to overcome difficulties that arise when the marginal likelihood involves integrals over random effects that do not have a closed-form solution. The study examines various numerical integration methods used in marginal likelihood estimation, with emphasis on Gaussian quadrature and Gauss-Hermite quadrature. The construction of quadrature rules and their role in approximating intractable integrals are discussed in detail, together with the use of modified Newton-Raphson procedures for maximising the approximated likelihood. In addition, Bayesian ideas are introduced in the context of predicting random effects, where empirical Bayes estimates (posterior means) are used to obtain cluster-specific predictions within the fitted models. These modelling methods are applied to a dance competition dataset. Since the dancing performance scores awarded by judges had a left skewed non-normal distribution, it was decided to categorise these scores to five ordinal response categories and analysed using multilevel logit models. The hierarchical structure is represented by individual performers (level-1 units) nested within dance types (level-2 units) allowing two-level models to be fitted. The models are implemented in Stata using the GLLAMM software, which provides flexible likelihood-based estimation for multilevel models with ordinal responses using numerical integration. The analysis demonstrates how multilevel models for ordinal responses can be used to account for clustering, estimate random-effects variability, compare alternative model structures, and interpret the effects of explanatory variables in a practically meaningful way. Overall, the paper provides a methodological and applied examination of multilevel modelling for ordinal categorical data. It shows that when ordinal responses are analysed within a hierarchical framework, likelihood-based estimation supported by quadrature methods offers a rigorous and practical approach for modelling complex dependence structures and obtaining interpretable statistical inferences. Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/147019 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/146965 Title: Distribution and microhabitat use of naturalised Common Chameleons, Chamaeleo chamaeleon (Linnaeus, 1758), in Malta Authors: Farrugia, Kristyl; Borg, Joseph A.; Schembri, Patrick J. Abstract: The Common Chameleon, Chamaeleo chamaeleon, was introduced to Malta in the mid-19th century and is now fully naturalised, yet detailed ecological information for the Maltese archipelago remains very limited. This study provides the first integrated assessment of its spatial and seasonal distribution, microhabitat use, and age-related patterns of variation using systematic field surveys across 13 sites. Abundance varied markedly among regions, with northern sites supporting the highest densities, likely reflecting greater availability of semi-natural and suburban vegetation. Seasonal differences in abundance were minimal, although winter surveys indicated reduced detectability. Chameleons showed strong associations with coniferous vegetation and mid-height perches (101–300 cm), with seasonal shifts consistent with thermoregulatory demands. Ontogenetic patterns indicated partial niche partitioning, with smaller individuals occupying lower and occasional peripheral branches, while larger individuals used higher and more central positions. Overall, the species’ adaptability to fragmented landscapes and human-modified habitats explains its successful establishment in Malta, while emphasising the importance of maintaining tree-rich green spaces for long-term population persistence. Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/146965 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/146844 Title: A new alien arrival to the Sicilian coast of the Ionian Sea : Trachysalambria palaestinensis (Steinitz, 1932) Authors: Tiralongo, Francesco; Leotta, Paola; Marrone, Alessio; Deidun, Alan Abstract: Trachysalambria palaestinensis, a penaeid shrimp native to the Red Sea, Gulf of Oman, and Persian Gulf, has recently expanded its distribution within the Mediterranean Sea as part of the ongoing Lessepsian migration process. Here we provide the first confirmed records of this species from the Ionian sector of Sicily, representing not only the first evidence for the Sicilian Ionian coast, but also the first documented occurrence in the Ionian Sea at large. The species was recorded on four separate occasions between 2021 and 2025 from trammel net fisheries targeting cuttlefish (Sepia officinalis). Morphological analysis confirmed species identification. Specimens were deposited in the scientific collection of the Ente Fauna Marina Mediterranea located in Avola, Italy. These findings draw further attention to the growing number of Indo-Pacific crustaceans colonizing Mediterranean ecosystems. We discuss the biogeographical significance of this record, the possible ecological implications for native assemblages and fisheries, and the need for long-term monitoring. Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/146844 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/146818 Title: New records of marine biodiversity in the Mediterranean Sea (April 2026) Authors: Zenetos, Argyro; Abd El-Gwaad, Fares Nasser; Al-Beak, Ahmed Mohamed; Antit, Mouna; Baldacchino, Yacopo; Barría, Claudio; Ćetković, Ilija; Costa, Maurizio; Crocetta, Fabio; Đorđević, Nikola; Fitori, Amani; Bella S., Galil; Galiya, Mohamad Younes; Golani, Daniel; Joksimović, Aleksandar; Leban, Neža; Leotta, Paola; Mačić, Vesna; Marković, Olivera; Orenes-Salazar, Víctor; Othman, Ranim Mohamad; Pujol, Juan A.; Rizgalla, Jamila; Sedano, Francisco; Stanić, Rino; Tanduo, Valentina; Taşkın, Ergün; Travaglini, Andrea; Tiralongo, Francesco; Trabelsi, Aya; Trkov, Domen; Ugarković, Pero; Vella, Adriana; Vella, Noel; Yazılan, Öznur Abstract: This collective article presents new information about 18 species occurring in 12 Mediterranean countries from the Alboran Sea to the Levantine Sea. Five lessepsian species namely Erugosquilla massavensis, Syrnola fasciata, Plocamopherus ocellatus, Maritigrella fuscopunctata and Siganus javus have spread within 2025 to neighbouring MSFD areas. Another five are here reported as first country records [Polyandrocarpa zorritensis (Malta), Gonioinfradens giardi (Italy), Istiblennius meleagris (Egypt), Epinephelus fasciatus (Israel), Lophocladia trichoclados (Montenegro)]. Cladophora patentiramea has spread from the Levantine to the Aegean Sea, while Pinctada radiata has reached Granada, and Cádiz. The Atlantic fish Enchelycore anatina and Synodus synodus have expanded their distribution to Montenegro and Syria respectively. Three rare native species are reported for first time at country level, while a fourth (Mobula birostris) has made an appearance more than a century after its first Mediterranean record. Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/146818 2026-01-01T00:00:00Z