While traditional psychologists specializing in close relationships have focused on relationship dysfunction, positive psychology argues that relationship health is not merely the absence of relationship dysfunction.  Healthy relationships are built on a foundation of secure attachment and are maintained with love and purposeful positive relationship behaviors. Additionally, healthy relationships can be made to "flourish." Positive psychologists are exploring what makes existing relationships flourish and what skills can be taught to partners to enhance their existing and future personal relationships. A social skills approach posits that individuals differ in their degree of communication skill, which has implications for their relationships. Relationships in which partners possess and enact relevant communication skills are more satisfying and stable than relationships in which partners lack appropriate communication skills. 
Symbiosis played a major role in the co-evolution of flowering plants and the animals that pollinate them. Many plants that are pollinated by insects , bats , or birds have highly specialized flowers modified to promote pollination by a specific pollinator that is also correspondingly adapted. The first flowering plants in the fossil record had relatively simple flowers. Adaptive speciation quickly gave rise to many diverse groups of plants, and, at the same time, corresponding speciation occurred in certain insect groups. Some groups of plants developed nectar and large sticky pollen, while insects evolved more specialized morphologies to access and collect these rich food sources. In some taxa of plants and insects the relationship has become dependent,  where the plant species can only be pollinated by one species of insect.