Transcript nsect Ecology

Aquatic Ecology
How much water is there on
Earth?
Habitats and Communities
Marine systems: three major zones
1. Off shore or open sea
Devoid of insects
2. Neritic or near shore
3. Intertidal – alternately submerged and
exposed
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Few insects
some of great interest – discuss later
Habitats and Communities
Estuaries: brackish water
• Ecotone between inland water and the
sea
• Richer aquatic insect fauna than marine
Habitats and Communities
Lotic: inland running water
1. Crenal – spring fed headwaters
2. Rhithral – streams and small rivers
3. Potamal – large rivers
Highest diversity of aquatic insects
Habitats and Communities
Lentic: inland standing water
1. Lacustrine – lakes and ponds
2. Palustrine – marshes and swamps
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Shallow habitats
Ecotones between aquatic and terrestrial
Greatest insect diversity associated with vegetation
Habitats and Communities
Subterranean waters: Hypogean
1. Troglal – caves
2. Stygal – groundwater
Relatively sparse insect communities
except were merging with surface
waters
Habitats and Communities
Biotic Community:
• Comprises all populations in a given
habitat -- including everything from
bacteria to vertebrates and higher
plants
Habitats and Communities
“Planktonic Community”
• Plankton – organisms that remain
suspended
• Adaptations for vertical migration and/or
to remain at certain depths
Few insects adapted to planktonic
existence
Habitats and Communities
“Nektonic Community”
• Nekton – Strong swimmers not at the
mercy of the currents.
Few insect representatives
Habitats and Communities
“Pleustonic Community”
• Pleuston – Organisms at air-water
interface
Atmospheric breathers that require
aqueous medium for other needs
Habitats and Communities
“Benthic Community”
• Benthos – organisms associated with
substratum
• Bottom materials, plant beds, logs or
other solid surfaces
Lentic Freshwaters
• Lakes provide diverse habitats for aquatic
insects
• Environmental conditions
– Distinct spatial gradients
– Temporal changes pronounced
Aquatic insect communities change w/
gradients in lakes and between lake types
Lake Zonation
• Limnetic Zone – open water devoid of rooted
vegetation
• Littoral Zone – shallow marginal areas
characterized by rooted vegetation
• Sublittoral Zone – transition between wellilluminated upper strata and Profundal Zone
• Profundal Zone – light insufficient for
photosynthesis
Lake Zonation
Lake Communities
Pleuston: organisms associated with
surface film
• Epipleuston – upper surface
– Water striders
• Hypopleuston – lower surface
• Meropleuston – not continuous resident
– Mosquito larvae
Lake Communities
Pleuston:
• Adaptations for surface residence
– Small size
– Furcula
• Collembola
– Hydrophobic cuticle
• Gyrinids have hydrophobic dorsum and wettable venter
Lake Communities
Pleuston:
• Three families of Hemiptera = striders
– Hydrometridae – elongate body and legs
• Water measurer
– Gerridae and Veliidae
• Supported by full length of tarsi
• Tarsi covered with “hairpiles”
• Secrete substance that lowers surface tension
Lake Communities
• Pleuston:
• Diptera limited to mosquitoes
• Hydrophilid beetles “walk” inverted on
underside of water surface
Lake Communities
Plankton:
• Insects poorly represented
• Chaoboridae only planktonic insect
Lake Communities
Chaoboridae:
• World wide
– Lakes and ponds
• Nearly transparent
• Prehensile antennae
• Feed on zooplankton and mosquitoes
Lake Communities
Chaoborus:
• Tracheal system reduced to kidney
shaped air sacs
– One pair thoracic; another in abdomen
• Use these “hydrostatic organs” to adjust
buoyancy
Lake Communities
Chaoborus:
• 2 types of vertical migration
– Full – generally in lake species
• Reside in bottom mud during day
• Feed in water column at night
– Reduced – predominately in pond species
= Remain in epilimnion
Lake Communities
Chaoborus:
• Limited migration of some species may
explain why they are missing from lakes
with fish (C. americanus)
• Others coexist with fishes (full), and are
found in fishless lakes (reduced; C.
flavicans)
Lake Communities
Chaoborus:
• Different larval instars exhibit different
migratory behavior
C. trivittatus
– 1st and 2nd instars restricted to surface
water
– 3rd and 4th move to deeper water during
day
– Smallest at surface, size  with depth
Lake Communities
Chaoborus:
– Regular depth distribution of size classes
apparently related to food size distribution
and predation
• Larger items generally deeper
• Greater vulnerability to visual predation
Lake Communities
Chaoborus:
• Light = entraining agent
– Benthic & planktonic phases can be
artificially reversed in lab
– instars react differently
Lake Communities
Chaoborus:
• Oxygen = entraining agent
– High 02 1% migrated
– Low 02 30% migrated
Lake Communities
Chaoborus:
• Horizontal migration
– Spring migration of larvae to littoral zone
– Adaptation enabling exposure to warm
water prior to pupation
http://cfb.unh.edu/CFBkey/html/m
ovies.html#
Lake Communities
Chironomidae:
• 1st instar adapted to planktonic
existence for dispersal
– Larvae positively phototactic 1-3 days
– Vertical migrations common w/ diel light
– As larvae mature shift from photophilous to
photophobic
Lake Communities
Chironomidae:
• Late instars may again enter plankton
1. Move to well-aerated water
2. In some species, late instar individuals
follow pattern described for 1st instars
Lake Communities
Ranatra montezuma:
Hemipteran
• Nocturnal planktonic behavior
• As light drops below 100 lux, move from
littoral to limnetic zone
• Feed on Hyalella montezuma, return to littoral
zone during day
Lake Communities
Nekton:
• Nekton distinguished from plankton by
directional mobility; from benthos by
association with open water
• Although many aquatic insects swim,
they are associated with hard substrate
Lake Communities
Nekton:
• Truly nektonic species restricted to a
few hemipterans and coleopterans
• Hemiptera nektonic species include
Notonectidae, Corixidae and
Belostomatidae
Lake Communities
Nekton:
• Anisops and Buenoa (Notonectidae)
use hemoglobin to control buoyancy
• Prey on small arthropods in open water
column
Lake Communities
Nekton:
• Relationship between habitat and leg structure
– Buenoa – open water
– Hind legs for rapid pursuit
– Forelegs and midlegs for prey capture
Lake Communities
Nekton:
• Relationship between habitat and leg
structure
– Notonecta – underside of surface film
• Feed on moving prey as well as those caught in
surface film
• Leg structure is intermediate
Lake Communities
Nekton:
• Corixidae
+ Elongate, flattened, hair-fringed hindlegs
+ Most restricted to water < 1 m
Planktivorous spp. are nektonic
Lake Communities
Nekton:
• Belostomatidae
– Most are sit and wait predators
– Lethocerus = nekton
• Coleoptera
– Only largest Dytiscidae and Hydrophilidae
Lake Communities
Benthos:
• Majority of insects in lentic habitats are
benthic
• Collectively, aquatic insects make up to 90%
of total benthic fauna
Lake Communities
Benthos:
• Several orders have highest diversity and
abundance in lentic habitats
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Odonata (dragonflies)
Hemiptera
Coleoptera
Diptera (some families exclusively lentic)
Hymenoptera
Lepidoptera
Neuroptera
Lake Communities
Benthos:
• The composition and relative
abundance of aquatic insects is
integrated along depth profiles
Lake Communities
Benthos:
• Hutchinson - insect fauna of lakes fall
into three depth categories
1. Aquatic adults that never developed gills
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Hemipterans and coleopterans
– Rarely occur in water depth more than 3 m
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Most surface for air
Lake Communities
Benthos:
• Hutchinson - insect fauna of lakes fall
into three depth categories
2. All other orders with exception of Diptera
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Amphibiotic (aquatic larva, terrestrial adult)
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Extract O2 from water
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Restricted to relatively shallow water
Lake Communities
Benthos:
• Hutchinson - insect fauna of lakes fall into
three depth categories
3. Only certain dipterans have colonized profundal
zone
– Amphibiotic
– Chaoboridae
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Chironomidae
Lake Communities
• Taxonomic
richness of benthic
insect communities
declines with depth
• Max richness at
depths of 1-2 m
Exam topics
Hoeinghaus et al. 2007
• Which river concept explains energy
sources in 10 tribs of Parana’ river?
• Low-gradient, high gradient, reservoirs
• C,N isotopes for fishes, molluscs, plants,
detritus
• Big conclusions?
– Lowland river foodwebs = C from aquatic
macrophytes
– Reservoirs = C from algae more important
– High gradient rivers = C from filamentous
algae
Lytle and Poff 2004
•Adaptations to survive floods and droughts
•ID adaptations
•Modes: know examples
•Timing of flow = life history adaptations
•Predictability = behavioral adaptations
•Magnitude/freq = morphological adaptations
•Human impacts
Stone et al. 2005
•Macroinvertebrates of ag streams
•What variables impact them?
•Methods? Sites? Sampling? What attributes
were compared?
•Which attributes varied with physical
variables?
•What impacts caused low scores for
macroinvertebrates?
Merritt and Cummings
Chapter 3 Sampling
•Devices
•Sorting, preservation
•Taxonomic resolution
Merritt and Cummings
Chapter 5 Habitat, life history
•Marine paradox
•Hydraulics
•Habitats
•Upstream movements