Statistical mechanics of ecosystem assembly

We introduce a toy model of ecosystem assembly for which we are able to map out all assembly pathways generated by external invasions. The model allows to display the whole phase space in the form of an assembly graph whose nodes are communities of species and whose directed links are transitions between them induced by invasions. We characterize the process as a finite Markov chain and prove that it exhibits a unique set of recurrent states (the endstate of the process), which is therefore resistant to invasions. This also shows that the endstate is independent on the assembly history. The model shares all features with standard assembly models reported in the literature, with the advantage that all observables can be computed in an exact manner.Comment: Accepted for publication in Physical Review Letter

An Empirical Comparison of Beta Diversity Indices in Establishing Prairies

Whittaker (1960, 1972) first proposed the idea that species diversity has spatial components, with alpha diversity estimating diversity within individual stands (or communities) and beta diversity estimating the number of community types in an area (or in Whittaker’s terminology, ‘‘differentiation of communities along gradients’’). These two values combined make up gamma diversity. Beta diversity is important because it provides the conceptual link between local and regional diversity, more directly measures how soil types, disturbance, and dispersal affect diversity, and is helpful in understanding why species loss is sometimes smaller than predicted by theory (Wilsey et al. 2005). Many interesting and longstanding questions are applied across scales, such as how much diversity is found within islands vs. across islands? Is the number of habitat types (i.e., beta) within islands key to explaining diversity at larger scales or is it the greater population sizes found on large islands? Furthermore, a consideration of both alpha and beta is necessary for understanding how diversity arises and is maintained in diverse systems. For example, in the northern Great Plains, we have found that remnant prairies can contain over 120 plant species within a small area (Wilsey et al. 2005); this occurs because of high diversity at the neighborhood scale where 20–25 species are found per square meter (Martin et al. 2005), and from species accumulation across neighborhoods (i.e., beta)

Comparison of Odonata Populations in Natural and Constructed Emergent Wetlands in the Bluegrass Region of Kentucky

With the degradation and destruction of many natural wetlands in Kentucky, there are high incentives to look at the remaining natural wetlands and the new artificial wetlands that are beginning to become prevalent among biologists. Wetlands are important to dragonfly populations just as dragonflies are vital to wetland function. In my study I looked at the fluctuation in Odonata (dragonfly and damselfly) populations at ten artificial wetlands and ten natural wetlands in the Inner Bluegrass region of Kentucky. In my study the dragonfly populations were monitored based on Shannon and Simpson\u27s diversity, Species richness, and number of individual and species numbers. The wetlands were also compared on a season to season basis and the health of the wetlands were considered using a rapid assessment method. My research found that the artificial wetlands, though they scored low on the rapid assessment method, scored high in all categories except for species richness in the fall season of data collection. This study can be important in discovering the differences between natural and artificial wetlands, since Odonates are such an important biological indicator of wetland health and function. This could be vital in increasing the health of remaining natural wetlands and new artificial wetlands that are being created to supplement the lack of many of Kentucky\u27s natural wetlands

Species abundance patterns in an ecosystem simulation studied through Fisher's logseries

We have developed an individual-based evolving predator-prey ecosystem simulation that integrates, for the first time, a complex individual behaviour model, an evolutionary mechanism and a speciation process, at an acceptable computational cost. In this article, we analyse the species abundance patterns observed in the communities generated by our simulation, based on Fisher's logseries. We propose a rigorous methodology for testing abundance data against the logseries. We show that our simulation produces coherent results, in terms of relative species abundance, when compared to classical ecological patterns. Some preliminary results are also provided about how our simulation is supporting ecological field results

Can indices of ecological evenness be used to measure consensus?

In the context of group decision making with fuzzy preferences, consensus measures are employed to provide feedback and help guide automatic or semi-automatic decision reaching processes. These measures attempt to capture the intuitive notion of how much inputs, individuals or groups agree with one another. Meanwhile, in ecological studies there has been an ongoing research effort to define measures of community evenness based on how evenly the proportional abundances of species are distributed. The question hence arises as to whether there can be any cross-fertilization from developments in these fields given their intuitive similarity. Here we investigate some of the models used in ecology toward their potential use in measuring consensus. We found that although many consensus characteristics are exhibited by evenness indices, lack of reciprocity and a tendency towards a minimum when a single input is non-zero would make them undesirable for inputs expressed on an interval scale. On the other hand, we note that some of the general frameworks could still be useful for other types of inputs like ranking profiles and that in the opposite direction consensus measures have the potential to provide new insights in ecology

The world's richest tadpole communities show functional redundancy and low functional diversity: ecological data on Madagascar's stream-dwelling amphibian larvae

<p>Abstract</p> <p>Background</p> <p>Functional diversity illustrates the range of ecological functions in a community. It allows revealing the appearance of functional redundancy in communities and processes of community assembly. Functional redundancy illustrates the overlap in ecological functions of community members which may be an indicator of community resilience. We evaluated patterns of species richness, functional diversity and functional redundancy on tadpole communities in rainforest streams in Madagascar. This habitat harbours the world's most species-rich stream tadpole communities which are due to their occurrence in primary habitat of particular interest for functional diversity studies.</p> <p>Results</p> <p>Species richness of tadpole communities is largely determined by characteristics of the larval habitat (stream structure), not by adult habitat (forest structure). Species richness is positively correlated with a size-velocity gradient of the streams, i.e. communities follow a classical species-area relationship. While widely observed for other taxa, this is an unusual pattern for anuran larvae which usually is expected to be hump-shaped. Along the species richness gradient, we quantified functional diversity of all communities considering the similarity and dissimilarity of species in 18 traits related to habitat use and foraging. Especially species-rich communities were characterised by an overlap of species function, i.e. by functional redundancy. By comparing the functional diversity of the observed communities with functional diversity of random assemblages, we found no differences at low species richness level, whereas observed species-rich communities have lower functional diversity than respective random assemblages.</p> <p>Conclusions</p> <p>We found functional redundancy being a feature of communities also in primary habitat, what has not been shown before using such a continuous measure. The observed species richness dependent pattern of low functional diversity indicates that communities with low species richness accumulate functional traits randomly, whereas species in species-rich communities are more similar to each other than predicted by random assemblages and therefore exhibit an accumulation of stream-specific functional traits. Beyond a certain species richness level, therefore, stream-specific environmental filters exert influence whereas interspecific competition between species does not influence trait assemblage at any species richness level.</p

Biodiversity: Its Measurement and Metaphysics

Biodiversity is a concept that plays a key role in both scientific theories such as the species-area law and conservation politics. Currently, however, little agreement exists on how biodiversity should be defined, let alone measured. This has led to suggestions that biodiversity is not a metaphysically robust concept, with major implications for its usefulness in formulating scientific theories and making conservation decisions. A general discussion of biodiversity is presented, highlighting its application both in scientific and conservation contexts, its relationship with environmental ethics, and existing approaches to its measurement. To overcome the limitations of existing biodiversity concepts, a new concept of biocomplexity is proposed. This concept equates the biodiversity of any biological system with its effective complexity. Biocomplexity is shown to be the only feasible measure of biodiversity that captures the essential features desired of a general biodiversity concept. In particular, it is a well-defined, measurable and strongly intrinsic property of any biological system. Finally, the practical application of biocomplexity is discussed

Biodiversity: Its Measurement and Metaphysics

Biodiversity is a concept that plays a key role in both scientific theories such as the species-area law and conservation politics. Currently, however, little agreement exists on how biodiversity should be defined, let alone measured. This has led to suggestions that biodiversity is not a metaphysically robust concept, with major implications for its usefulness in formulating scientific theories and making conservation decisions. A general discussion of biodiversity is presented, highlighting its application both in scientific and conservation contexts, its relationship with environmental ethics, and existing approaches to its measurement. To overcome the limitations of existing biodiversity concepts, a new concept of biocomplexity is proposed. This concept equates the biodiversity of any biological system with its effective complexity. Biocomplexity is shown to be the only feasible measure of biodiversity that captures the essential features desired of a general biodiversity concept. In particular, it is a well-defined, measurable and strongly intrinsic property of any biological system. Finally, the practical application of biocomplexity is discussed

Wild bees diversity and abundance (Hymenoptera: Apoidea: Anthophila) in Lisbon urban gardens

Tese de mestrado, Ecologia e Gestão Ambiental, Universidade de Lisboa, Faculdade de Ciências, 2019Os polinizadores são conhecidos por fornecer diversos serviços de ecossistema, sendo a polinização o principal. Aproximadamente 80% de todas as espécies de plantas com flor são polinizadas por animais, maioritariamente por insetos. Este serviço é responsável por fornecer uma ampla variedade de alimentos, principalmente produtos hortícolas e frutas, dependendo essencialmente do mutualismo entre espécies, o polinizador e o indivíduo polinizado, resultado de relações complexas entre plantas e os polinizadores. Entre os polinizadores existentes, as abelhas são dos mais importantes, prestando um serviço de polinização avaliado em cerca de 153 mil milhões de euros por ano em todo o mundo e 22 mil milhões de euros por ano na Europa (Gallai et al. 2009). Este grupo depende quase exclusivamente de flores como fonte de proteínas, lipídios e açúcar durante o seu ciclo de vida (Michener 2007). Na Europa encontramos cerca de 10% da diversidade de abelhas em todo o mundo, esta grande biodiversidade é parcialmente explicada pela presença de áreas com clima Mediterrâneo (Michener 1979). Este facto pode ser explicado por duas razões: 1) energia e balanço hídrico mais favorável na que resulta numa diversidade floral elevada (Patiny et al. 2009); 2) O provável papel destas áreas como refúgios durante as glaciações do Quaternário (Reinig 1937, De Lattin 1967). Nos últimos anos, as múltiplas fontes de perturbação a este grupo, estão maioritariamente relacionadas com atividades antropogénicas (Arca et al. 2014, Ellis et al. 2010, Goulson et al. 2015, Henry et al., 2012, Kremen & Ricketts, 2002, Potts et al., 2006, Potts et al., 2010). Na Europa, a expansão e a intensificação agrícola, as alterações climáticas, a criação de gado intensiva, os pesticidas e o desenvolvimento urbano são dados como as principais ameaças às abelhas silvestres (Nieto et al. 2014). No entanto, grande parte das informações existentes sobre o declínio das abelhas provêm de perdas nas colónias de abelha-do-mel (Engelsdorp et al. 2008, Potts et al. 2010). De acordo com a Lista Vermelha Europeia de Abelhas (Nieto et al. 2014), existem cerca de 2000 espécies de abelhas identificadas na Europa, das quais 9% estão ameaçadas de extinção e 57% não possuem dados suficientes para avaliar o seu estado de conservação. As zonas urbanas são conhecidas por serem a principal fonte de destruição de habitat, nos quais as comunidades precisam de se adaptar às mudanças impostas pelas atividades humanas (Sattler et al. 2010). No entanto, estes ecossistemas trazem disponibilidade de locais de nidificação, qualidade e acessibilidade a diversas plantas (Ahrné et al. 2009, Frankie et al. 2005, McKinney 2008, e Ricketts et al. 2008). Nos últimos anos, estudos têm mostrado que muitos fatores bióticos e abióticos presentes nas cidades, ou em outros habitats urbanizados podem ter um impacto positivo na diversidade e abundância de abelhas (Ahrné et al. 2009, Banaszak-Cibicka 2013, Frankie et al. 2005, Potts et al., 2005, Smith et al., 2006). Estes locais geralmente fornecem uma produção contínua de néctar e pólen a partir da qual as abelhas se alimentam (Fussell & Corbet 1992, Osborne et al. 2008). Este estudo foi realizado na área metropolitana de Lisboa, com início em Abril e com duração de 4 meses até Julho de 2018. Nos últimos anos, Lisboa aumentou a quantidade de espaços verdes, como espaços hortícolas que muitas vezes estão associados a parques urbanos. Este estudo tem incidência em três hortas comunitárias: Quinta da Granja (QG), Quinta Conde d’Arcos (QCA) e Quinta das Flores (QF). Os locais de estudo foram escolhidos por apresentarem meios envolventes idênticos e serem geridos por particulares sob jurisdição do governo local. Este estudo utilizou três diferentes métodos de amostragem: 1) Capturas com rede entomológica; 2) “Pan-trap”; 3) “Trap-nest” (Wesphal et al. 2008). Estes métodos foram utilizados combinados para aumentar a quantidade de dados devido ao curto período disponível para o estudo. Foram identificadas 57 espécies provenientes dos batimentos com rede entomológica, das quais cinco são consideradas raras em Portugal: Andrena florentina (M.), Andrena livens (E.), Hylaeus dilatatus (K.), Hylaeus hyalinatus (S.) e Megachile ericetorum (L.). O local que registou o maior número de espécies de abelhas foi a Quinta da Granja (31 espécies), seguida pela Quinta das Flores (29 espécies) e por último a Quinta Conde d’Arcos (25 espécies). A família Megachilidae foi a mais diversificada, apresentando cinco géneros e 16 espécies diferentes, no entanto a família Apidae foi a mais abundante. A espécie mais frequente foi a Lasioglossum maluchurum (K.) com 17 espécimes capturados. O melhor modelo que explicou a riqueza e abundância de abelhas silvestres, nos três locais, conteve apenas a riqueza florística entre todas as variáveis ambientais computadas. Medidas de gestão foram sugeridas para melhorar os serviços de ecossistemas fornecidos pelas abelhas silvestres nas áreas urbanas. É urgente entender como podemos melhorar estes habitats para os polinizadores, uma vez que o resultado será benéfico para todos, insetos, plantas e para nós Humanos. Dada a falta de estudos atuais sobre a diversidade de abelhas silvestres em Portugal, juntamente com as crescentes ameaças a este grupo de polinizadores, espera-se que este documento enriqueça o conhecimento atual existente.Pollination is the service responsible for a wide variety of food, mainly horticultural crops and orchards, being a key process in both human managed and natural terrestrial ecosystems. It is known that this service is declining abruptly, mainly due to the different anthropogenic pressures. Bees among pollinators provide an ecosystem service, on crop pollination, estimated in 153 billion euros a year worldwide and 22 billion euros a year in Europe. However, the lack of distinction between the declines of wild pollinators and honeybees is usually misunderstood, leading to focus mainly on the most common social species such as Apis mellifera (L.) and Bombus terrestris (L.). In the last 10 years, attention has been drawn to the positive impact of urban gardens and allotment gardens on wild pollinators consequently on the pollination service. In this study, the main goal was to address wild bee diversity and abundance in three urban gardens inside Lisbon metropolitan area. It was also intended to understand which variables could explain better bee diversity and abundance at the three locations. The 202 specimens collected, comprised 5 families, 18 genera and 57 species, having five species considered rare in Portugal and ten first records for the Lisbon district. The best model explaining wild bee richness and abundance, across the three sites, contained only flower richness among all environmental variables computed. Management measures were suggested to improve ecosystem services provided by wild bees in these urban areas. It is urgent to understand how we can improve these habitats for pollinators, once the outcome could be beneficial for all, insects, plants and for us Humans