Ecological characterizations of cytotypes of the Simulium venustum-verecundum complex (Diptera- simuliidae) found on the Avalon Peninsula, Newfoundland

McCreadie, John William (1991) Ecological characterizations of cytotypes of the Simulium venustum-verecundum complex (Diptera- simuliidae) found on the Avalon Peninsula, Newfoundland. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (38MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The S. venustum/verecundum complex (Avalon Peninsula,Newfoundland) was examined to ascertain if individualcytotypes had unique and predictable ecological characteristics. Emphasis was placed on larval spatial-temporal distribution. Six cytotypes were found: EFG/C venustum, CC2-3 venustum (combined CC2 and CC3), AC(gb) venustum. AA verecundum and ACD verecundum. -- Larval cytotypes selected different macrohabitats. EFG/C and ACD were sublacustrine species; CC2-3 and AC(gb) preferred downstream sites. Within downstream habitats CC3 usually occurred in large streams and AC(gb) in cool canopied sites with a bed of small stones or rubble; CC2 was ubiquitous. AA preferred outlets and trickles. Cytotype fauna changed in a continuous, directional and predictable manner with increased distance from outlets. -- Abundance of CC2-3 increased with increasing seston and- discharge, and decreasing conductivity. AC(gb) abundance increased with increasing stream width. -- Larval cytotypes also selected different microhabitats. Optimal velocity for EFG/C and ACD was 0.36 and 0.71 m/s, respectively. EFG/C preferred shallow water but ACD showed no depth preference. These differences were not related to larval size. Maximum abundance of EFG/C occurred 10.5 - 16.O m from outlets; ACD was most abundant just below outlets. Proportionally more ACD and AA were found on vegetation than rocks; the reverse was true for EFG/C. The density of ACD and AA was higher on vegetation than rocks. -- Seasonal occurrence of cytotypes overlapped but population peaks were typically asynchronous. EFG/C appeared 1-5 weeks earlier than other cytotypes. ACD and AA appeared later and remained longer than other cytotypes. EFG/C was univoltine. AC(gb) may have a limited second generation. CC2-3 was bi- or multivoltine. ACD and AA were multivoltine. -- EFG/C complete larval development from 5 - 30°C with maximum survival between 15 - 20°C (68.0 - 73.5%). An ACD-AA mixed population completed development between 5 - 25°C with maximum survival between 15 - 25°C (55.3 - 61,0%) . The temperature survival curve of EFG/C was significantly different from ACD-AA. Threshold temperature was 0°C. Degree- days to complete larval development varied with temperature, cytotype and sex. Temperature also affected larval size. -- It was concluded that each cytotype examined was a distinct species with a unique and predictable ecological profile, supporting the hypothesis of widespread sibling speciation within the S. venustum/verecundum complex.

Actions (login required)

View Item