Presentation on theme: "Relationships Between Habitat Preferences, Feeding, Life Cycles of Aquatic Insects & Stream Health Dr. Robert Bohanan University of Wisconsin - Madison."— Presentation transcript:
Relationships Between Habitat Preferences, Feeding, Life Cycles of Aquatic Insects & Stream Health Dr. Robert Bohanan University of Wisconsin - Madison Center for Biology Education
Homage to Santa Rosalia or Why are there so many different kinds of animals? G. E. Hutchinson, 1959 “… Vast numbers of Corixidae were living in the water. At first I was rather disappointed because every specimen of the two species present was a female, and so lacking in most critical diagnostic features, while both sexes of the second slightly smaller species were present in about equal number. … The larger C. punctata was clearly at the end of its breeding season, the smaller C. affinis was probably just beginning to breed. This is the sort of observation than any naturalist can and does make all the time. It was not until I asked myself why the larger species should breed first, and then the more general question as to why there should be 2 and not 20 or 200 species of the genus in the pond, that ideas suitable to present to you began to emerge. These ideas prompted the very general question as to why there are such an enormous number of animal species.”
Aquatic Insects Inhabit Virtually Every Possible Freshwater Habitat What are some of the factors that might explain why insects have been so successful in freshwater? –Evolutionary history –Morphology –Physiology –Behavior –Development
What living and non-living factors could influence the successful development of an organism from an egg to a sexually reproducing adult in a stream?
How might habitat selection affect the life history of an aquatic insect? Substrate for attachment and or shelter Food availability (quality and quantity) Range of current Water temperature and Oxygen Presence and relative abundance of other organisms Others?
Table 2. Substrate TypeAbundance (#/m 2 ) # of Species Sand Gravel Pebbles & Cobble Leaves Detritus Graphic presentation of Table 2. Abundance (# / square meter) (x) # of species (o) SandGravel Pebbles & Cobble Leaves Detritus o o o o o x x x x x
Where’s the Mayfly?
Most Aquatic Insects Include a Sexually Mature Winged Adult
Burrowing and Clinging
Staying Out of the Current
Common Mayfly Habitat Preferences Baetidae Heptageniidae Caenidae Slow - Fast Current, Pools-Riffles, Variety of Substrate Slow-Fast Current, Often in Cobble, Logs, Submersed Vegetation, Leaf Packs Slower Current, Sediments
Mayfly Life History Baetidae Heptageniidae Caenidae Ephemeridae Ephemerellidae Leptohyphidae Potamanthidae Isonychidae Often Bivoltine Mostly Univoltine Likely Univoltine Univoltine, some Semivoltine Univoltine Univoltine, some Bivoltine/Multi Univoltine Bivoltine, some Univoltine
Filter Feeding Using Nets
How do caddisflies share what may be limited resources? Habitat selection Substrate preferences Resource partitioning –Shredders –Filterers –Collectors –Predators
Caddisfly Life History Hydropsychidae Limnephilidae Hydroptilidae Helicopsychidae Uenoidae Brachycentridae Glossosomatidae Psychomyiidae Philopotamidae Phryganeidae Univoltine, some Bivoltine-Semi Univoltine Univoltine, some Bivoltine Likely Univoltine Semivoltine, some Univoltine Univoltine Likely Univoltine Univoltine
Territoriality and Foraging Caddisfly larvae include case- building species Larvae scrape algae from the surface of rocks in streams and rivers What is the relationship of territory size and larval growth?
Why Build Cases? Tube-shaped cases appear in Diptera (above) and in Trichoptera (below)
Case building in some insect larvae reduces encounter rates and mortality Some case building species had reduced encounter frequency than did some non- case building species Lower encounter frequency also resulted in lower mortality of case builders compared to non-case builders
Evolutionarily, why do some species build cases and others not? Cases may not be adaptive, may be a byproduct Cases may be adaptive, but for some species the costs may exceed the benefits What are some potential costs?
Evolutionary Costs of Case Construction Building additional cases increases larval mortality Building additional cases prolongs larval development Building additional cases as larvae reduces the number of eggs in adult females