Biological Diversity PDF

BIOLOGICAL DIVERSITY WHAT IS BIODIVERSITY?  The variety of life on Earth.  The totality of genes, species, and habitats in a region.  BIODIVERSITY AND EVOLUTION  Speciation and extinction events continuously changes global levels of diversity HOW MANY SPECIES AR...

BIOLOGICAL DIVERSITY WHAT IS BIODIVERSITY?  The variety of life on Earth.  The totality of genes, species, and habitats in a region.  BIODIVERSITY AND EVOLUTION  Speciation and extinction events continuously changes global levels of diversity HOW MANY SPECIES ARE THERE?  ~ 8.7 million species of eukaryotes (Mora et al., 2011)  Only 1.2 million species had been catalogued  86% of terrestrial species and 91% of marine species are still waiting discovery  ~ 1 trillion species of prokaryotes (Locey & Lennon, 2016)  ~ 300,000 fossil species discovered so far ( 20,940 70% Corals 462 3% Molluscs ~20,000 ----- Marine Fishes 2,241 Freshwater 4% 209 Fishes Amphibians 118 84% Reptiles 378 78% Birds 714 36% Mammals 233 50% ESTIMATED NUMBER OF PLANT SPECIES Plant Group Estimated No. Endemics Angiosperms 8,120 5,800 (71%) Gymnosperms 33 6 (18%) Pteridophytes 1,100 285 (26%) Bryophytes 1,271 195 (15%) Algae 1,355 ----- Sources: Gruezo, 1979; DENR-UNEP, 1997; Villareal and Fernando, 2000; Barcelona, 2002; Fernando, 2006 WHY IS THE PHILIPPINES BIOLOGICALLY DIVERSE? PHILIPPINES’ HIGH BIODIVERSITY IS DUE TO:  The complex geological history of its islands with long periods of isolation A dynamic sequence of landscape fragmentation and coalescence of landmasses due to:  Periodic sea-level oscillations  Plate tectonics resulting in the coalescence of land masses  Last Glacial Maximum (~20,000 years ago) Present Day Tectonic features of Luzon coincides with recognized biotic regions (Source: Vallejo, 2014) A biota that is derived from two distinct biogeographic regions of the planet – Oriental and Australian  Species affinities between:  Palawan and mainland Asia  Batanes, Cagayan, and Taiwan  Mindanao, Sulu, and Borneo  Autochthonous diversification and speciation of ancestral species stocks within the archipelago;  Populations evolved to occupy different microhabitats;  The presence of isolating mechanisms resulted in the evolution of many unique and endemic lineages.  Autochthonous speciation among Philippine Monitor Lizards (Source: Welton et al., 2014) Autochthonous speciation of Platymantis frog in karst habitat (e.g. Biak na Bato National Park) WHAT FACTORS AFFECT AN AREAS’ BIODIVERSITY?  ABIOTIC FACTORS BIOTIC FACTORS  Climate  Availability of resources  Precipitation  Food  Temperature  Nesting sites  Topography  Mates  Elevation  Ecosystem Engineers  Sunlight  Competition  Hydrology  Human presence  Soil quality/ Substrate Type  Microhabitat Structure  Physical Structure of the Habitat Consumers Producers Microbiota CLIMATE: TEMPERATURE AND PRECIPITATION  Have a direct effect on vegetation in an area.  Most of the world’s biological diverse regions are in the tropics. TOPOGRAPHY: ELEVATION  Have a direct effect on temperature and precipitation  For every 1000m increase in elevation there is a decrease of 6.5°C  Notable observations in the Philippines:  An increase in endemic small, non-volant mammals as elevation increases (Heaney, 2001)  A decrease in fruit bat diversity as elevation increases (Alviola et al., 2011)  A decrease in herpetofaunal diversity as elevation increases (Gonzalez & Dans, 1997; Gojo Cruz et al., 2019)  Smaller plants in higher elevation. SUNLIGHT  Have a direct effect on the primary producers  The effect is most notable in aquatic habitats HYDROLOGY  Refers to all forms of bodies of water in an area  Have direct effects on species: as a resource and as a habitat  Also play an important role in nutrient cycling and transport (e.g. rivers to ocean) SOIL QUALITY AND SUBSTRATE TYPE  Have a direct effect on vegetation  Examples:  Carnivorous plants often thrive in nutrient-poor soil  Mangroves such as Avicennia sp. prefer muddy substrate, while Rhizophora sp. prefer sandy, muddy, or rocky substrates  Seagrass beds are often associated with sandy to rocky substrates  Limestone forest have lower number of dipterocarp species compared to sites with other substrates. BIOTIC FACTORS  Diversity increases with increasing resource availability.  More resources means reduced intra- and inter-specific competition reducing niche overlap ECOSYSTEM ENGINEERS  Species that creates, modifies, or maintains a habitat.  Two types:  Autogenic engineers – modify the environment by modifying themselves  E.g. plants, corals, seagrass  Allogenic engineers – modify the environment by changing the biotic and abiotic component of the habitat  E.g. earthworms, birds, beavers, fungi, humans Thiel, S., Tschapka, M., Heymann, E. W., & Heer, K. (2021). Vertical stratification of seed‐dispersing vertebrate communities and their interactions with plants in tropical forests. Biological Reviews, 96(2), 454-469. HUMANS AND BIODIVERSITY  Humans affect diversity by:  Reducing species richness and abundance (through accidental or intentional mortality)  Introducing species through human-mediated dispersal  Altering the habitat structure – turning complex habitats to simpler habitats  Reducing resources  Introducing chemicals that alter the physico-chemical structure of a habitat