When the transmitter does a Join for the first time, the Spreading Factor is set to SF12 and the bandwidth is set to BW125. This is DR0 according to the LoRaWAN specification. The transmitter will not adapt its Spreading Factor unless it receives a LinkADRReq from the gateway, asking it to use a different SF parameter.
The gateway's LinkADRReq is the only way the device can adjust the transmit power or data rate.
In proprietary LoRa mode, there is no ADR.