page_title: Density dependence
section_title: Examples
hierarchical_section_title: Density dependence / Negative density-dependence / Examples
context_page_description: In population ecology, density-dependent processes occur when population growth rates are regulated by the density of a population.
context_section_description: Density-dependent fecundity exists, where the birth rate falls as competition increases. In the context of gastrointestinal nematodes, the weight of female Ascaris lumbricoides and its rates of egg production decrease as host infection intensity increases. Thus, the per-capita contribution of each worm to transmission decreases as a function of infection intensity.
   Parasite-induced vector mortality is a form of negative density-dependence. The Onchocerciasis life cycle involves transmission via a black fly vector. In this life-cycle, the life expectancy of the black fly vector decreases as the worm load ingested by the vector increases. Because O. volvulus microfilariae require at least seven days to mature into infective L3 larvae in the black fly, the worm load is restricted to levels that allow the black fly to survive for long enough to pass infective L3 larvae onto humans.
caption: Density-dependent fecundity
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